In using Oovium to do some accounting reconciliation, I encountered an unexpected round off error with the sum of three terms (a, b, c) with one term negative (c). The order used in summing the terms makes a difference (i.e. a+b+c versus c+b+a or a+c+b).
The particular case is below:
y: a+b+c [yielding 4,811,824.18]
y-d: 9.3132257e-10 [expecting 0]
If y is reordered to c+a+b, y-d=0 without rounding error.