diff --git a/src/ripple/basics/Number.h b/src/ripple/basics/Number.h
index ead0e4321..cc009fa2e 100644
--- a/src/ripple/basics/Number.h
+++ b/src/ripple/basics/Number.h
@@ -149,7 +149,17 @@ public:
         return os << to_string(x);
     }
 
+    // Thread local rounding control.  Default is to_nearest
+    enum rounding_mode { to_nearest, towards_zero, downward, upward };
+    static rounding_mode
+    getround();
+    // Returns previously set mode
+    static rounding_mode
+    setround(rounding_mode mode);
+
 private:
+    static thread_local rounding_mode mode_;
+
     void
     normalize();
     constexpr bool
@@ -308,6 +318,9 @@ power(Number const& f, unsigned n);
 Number
 root(Number f, unsigned d);
 
+Number
+root2(Number f);
+
 // Returns f^(n/d)
 
 Number
diff --git a/src/ripple/basics/impl/Number.cpp b/src/ripple/basics/impl/Number.cpp
index 10834f08e..0690be077 100644
--- a/src/ripple/basics/impl/Number.cpp
+++ b/src/ripple/basics/impl/Number.cpp
@@ -23,6 +23,7 @@
 #include <numeric>
 #include <stdexcept>
 #include <type_traits>
+#include <utility>
 
 #ifdef _MSVC_LANG
 #include <boost/multiprecision/cpp_int.hpp>
@@ -33,6 +34,20 @@ using uint128_t = __uint128_t;
 
 namespace ripple {
 
+thread_local Number::rounding_mode Number::mode_ = Number::to_nearest;
+
+Number::rounding_mode
+Number::getround()
+{
+    return mode_;
+}
+
+Number::rounding_mode
+Number::setround(rounding_mode mode)
+{
+    return std::exchange(mode_, mode);
+}
+
 // Guard
 
 // The Guard class is used to tempoarily add extra digits of
@@ -107,16 +122,40 @@ Number::Guard::pop() noexcept
     return d;
 }
 
+// Returns:
+//     -1 if Guard is less than half
+//      0 if Guard is exactly half
+//      1 if Guard is greater than half
 int
 Number::Guard::round() noexcept
 {
-    if (digits_ > 0x5000'0000'0000'0000)
-        return 1;
-    if (digits_ < 0x5000'0000'0000'0000)
-        return -1;
-    if (xbit_)
-        return 1;
-    return 0;
+    auto mode = Number::getround();
+    switch (mode)
+    {
+        case to_nearest:
+            if (digits_ > 0x5000'0000'0000'0000)
+                return 1;
+            if (digits_ < 0x5000'0000'0000'0000)
+                return -1;
+            if (xbit_)
+                return 1;
+            return 0;
+        case towards_zero:
+            return -1;
+        case downward:
+            if (sbit_)
+            {
+                if (digits_ > 0 || xbit_)
+                    return 1;
+            }
+            return -1;
+        case upward:
+            if (sbit_)
+                return -1;
+            if (digits_ > 0 || xbit_)
+                return 1;
+            return -1;
+    }
 }
 
 // Number
diff --git a/src/test/basics/Number_test.cpp b/src/test/basics/Number_test.cpp
index b5425a7bc..d7bd82648 100644
--- a/src/test/basics/Number_test.cpp
+++ b/src/test/basics/Number_test.cpp
@@ -26,6 +26,24 @@
 
 namespace ripple {
 
+class saveNumberRoundMode
+{
+    Number::rounding_mode mode_;
+
+public:
+    ~saveNumberRoundMode()
+    {
+        Number::setround(mode_);
+    }
+    explicit saveNumberRoundMode(Number::rounding_mode mode) noexcept
+        : mode_{mode}
+    {
+    }
+    saveNumberRoundMode(saveNumberRoundMode const&) = delete;
+    saveNumberRoundMode&
+    operator=(saveNumberRoundMode const&) = delete;
+};
+
 class Number_test : public beast::unit_test::suite
 {
 public:
@@ -338,39 +356,156 @@ public:
     {
         testcase("test_to_integer");
         using Case = std::tuple<Number, std::int64_t>;
-        Case c[]{
-            {Number{0}, 0},
-            {Number{1}, 1},
-            {Number{2}, 2},
-            {Number{3}, 3},
-            {Number{-1}, -1},
-            {Number{-2}, -2},
-            {Number{-3}, -3},
-            {Number{10}, 10},
-            {Number{99}, 99},
-            {Number{1155}, 1155},
-            {Number{9'999'999'999'999'999, 0}, 9'999'999'999'999'999},
-            {Number{9'999'999'999'999'999, 1}, 99'999'999'999'999'990},
-            {Number{9'999'999'999'999'999, 2}, 999'999'999'999'999'900},
-            {Number{-9'999'999'999'999'999, 2}, -999'999'999'999'999'900},
-            {Number{15, -1}, 2},
-            {Number{14, -1}, 1},
-            {Number{16, -1}, 2},
-            {Number{25, -1}, 2},
-            {Number{6, -1}, 1},
-            {Number{5, -1}, 0},
-            {Number{4, -1}, 0},
-            {Number{-15, -1}, -2},
-            {Number{-14, -1}, -1},
-            {Number{-16, -1}, -2},
-            {Number{-25, -1}, -2},
-            {Number{-6, -1}, -1},
-            {Number{-5, -1}, 0},
-            {Number{-4, -1}, 0}};
-        for (auto const& [x, y] : c)
+        saveNumberRoundMode save{Number::setround(Number::to_nearest)};
         {
-            auto j = static_cast<std::int64_t>(x);
-            BEAST_EXPECT(j == y);
+            Case c[]{
+                {Number{0}, 0},
+                {Number{1}, 1},
+                {Number{2}, 2},
+                {Number{3}, 3},
+                {Number{-1}, -1},
+                {Number{-2}, -2},
+                {Number{-3}, -3},
+                {Number{10}, 10},
+                {Number{99}, 99},
+                {Number{1155}, 1155},
+                {Number{9'999'999'999'999'999, 0}, 9'999'999'999'999'999},
+                {Number{9'999'999'999'999'999, 1}, 99'999'999'999'999'990},
+                {Number{9'999'999'999'999'999, 2}, 999'999'999'999'999'900},
+                {Number{-9'999'999'999'999'999, 2}, -999'999'999'999'999'900},
+                {Number{15, -1}, 2},
+                {Number{14, -1}, 1},
+                {Number{16, -1}, 2},
+                {Number{25, -1}, 2},
+                {Number{6, -1}, 1},
+                {Number{5, -1}, 0},
+                {Number{4, -1}, 0},
+                {Number{-15, -1}, -2},
+                {Number{-14, -1}, -1},
+                {Number{-16, -1}, -2},
+                {Number{-25, -1}, -2},
+                {Number{-6, -1}, -1},
+                {Number{-5, -1}, 0},
+                {Number{-4, -1}, 0}};
+            for (auto const& [x, y] : c)
+            {
+                auto j = static_cast<std::int64_t>(x);
+                BEAST_EXPECT(j == y);
+            }
+        }
+        auto prev_mode = Number::setround(Number::towards_zero);
+        BEAST_EXPECT(prev_mode == Number::to_nearest);
+        {
+            Case c[]{
+                {Number{0}, 0},
+                {Number{1}, 1},
+                {Number{2}, 2},
+                {Number{3}, 3},
+                {Number{-1}, -1},
+                {Number{-2}, -2},
+                {Number{-3}, -3},
+                {Number{10}, 10},
+                {Number{99}, 99},
+                {Number{1155}, 1155},
+                {Number{9'999'999'999'999'999, 0}, 9'999'999'999'999'999},
+                {Number{9'999'999'999'999'999, 1}, 99'999'999'999'999'990},
+                {Number{9'999'999'999'999'999, 2}, 999'999'999'999'999'900},
+                {Number{-9'999'999'999'999'999, 2}, -999'999'999'999'999'900},
+                {Number{15, -1}, 1},
+                {Number{14, -1}, 1},
+                {Number{16, -1}, 1},
+                {Number{25, -1}, 2},
+                {Number{6, -1}, 0},
+                {Number{5, -1}, 0},
+                {Number{4, -1}, 0},
+                {Number{-15, -1}, -1},
+                {Number{-14, -1}, -1},
+                {Number{-16, -1}, -1},
+                {Number{-25, -1}, -2},
+                {Number{-6, -1}, 0},
+                {Number{-5, -1}, 0},
+                {Number{-4, -1}, 0}};
+            for (auto const& [x, y] : c)
+            {
+                auto j = static_cast<std::int64_t>(x);
+                BEAST_EXPECT(j == y);
+            }
+        }
+        prev_mode = Number::setround(Number::downward);
+        BEAST_EXPECT(prev_mode == Number::towards_zero);
+        {
+            Case c[]{
+                {Number{0}, 0},
+                {Number{1}, 1},
+                {Number{2}, 2},
+                {Number{3}, 3},
+                {Number{-1}, -1},
+                {Number{-2}, -2},
+                {Number{-3}, -3},
+                {Number{10}, 10},
+                {Number{99}, 99},
+                {Number{1155}, 1155},
+                {Number{9'999'999'999'999'999, 0}, 9'999'999'999'999'999},
+                {Number{9'999'999'999'999'999, 1}, 99'999'999'999'999'990},
+                {Number{9'999'999'999'999'999, 2}, 999'999'999'999'999'900},
+                {Number{-9'999'999'999'999'999, 2}, -999'999'999'999'999'900},
+                {Number{15, -1}, 1},
+                {Number{14, -1}, 1},
+                {Number{16, -1}, 1},
+                {Number{25, -1}, 2},
+                {Number{6, -1}, 0},
+                {Number{5, -1}, 0},
+                {Number{4, -1}, 0},
+                {Number{-15, -1}, -2},
+                {Number{-14, -1}, -2},
+                {Number{-16, -1}, -2},
+                {Number{-25, -1}, -3},
+                {Number{-6, -1}, -1},
+                {Number{-5, -1}, -1},
+                {Number{-4, -1}, -1}};
+            for (auto const& [x, y] : c)
+            {
+                auto j = static_cast<std::int64_t>(x);
+                BEAST_EXPECT(j == y);
+            }
+        }
+        prev_mode = Number::setround(Number::upward);
+        BEAST_EXPECT(prev_mode == Number::downward);
+        {
+            Case c[]{
+                {Number{0}, 0},
+                {Number{1}, 1},
+                {Number{2}, 2},
+                {Number{3}, 3},
+                {Number{-1}, -1},
+                {Number{-2}, -2},
+                {Number{-3}, -3},
+                {Number{10}, 10},
+                {Number{99}, 99},
+                {Number{1155}, 1155},
+                {Number{9'999'999'999'999'999, 0}, 9'999'999'999'999'999},
+                {Number{9'999'999'999'999'999, 1}, 99'999'999'999'999'990},
+                {Number{9'999'999'999'999'999, 2}, 999'999'999'999'999'900},
+                {Number{-9'999'999'999'999'999, 2}, -999'999'999'999'999'900},
+                {Number{15, -1}, 2},
+                {Number{14, -1}, 2},
+                {Number{16, -1}, 2},
+                {Number{25, -1}, 3},
+                {Number{6, -1}, 1},
+                {Number{5, -1}, 1},
+                {Number{4, -1}, 1},
+                {Number{-15, -1}, -1},
+                {Number{-14, -1}, -1},
+                {Number{-16, -1}, -1},
+                {Number{-25, -1}, -2},
+                {Number{-6, -1}, 0},
+                {Number{-5, -1}, 0},
+                {Number{-4, -1}, 0}};
+            for (auto const& [x, y] : c)
+            {
+                auto j = static_cast<std::int64_t>(x);
+                BEAST_EXPECT(j == y);
+            }
         }
         bool caught = false;
         try