I think that's just part of the process of deciding how small an increment each integer represents (dollars, cents, centi-cents, milli-cents).

Accounting rules often care more about consistency than precision per se. As long as the code follows accepted accounting rules (say bankers rounding) choosing a known precision works. Often GAAP and other standards don’t define all details for, say amortization, but if you use a scheme the code should always use that method.