fix: Fix IOU precision issues in LoanBrokerCover transactions (#7274)

src/libxrpl/protocol/STAmount.cpp

@@ -1738,4 +1738,9 @@ divRoundStrict(STAmount const& num, STAmount const& den, Asset const& asset, boo
     return divRoundImpl<NumberRoundModeGuard>(num, den, asset, roundUp);
 }
 
+[[nodiscard]] bool
+STAmount::isZeroAtScale(int scale) const
+{
+    return roundToScale(*this, scale, Number::RoundingMode::ToNearest).signum() == 0;
+}
 }  // namespace xrpl