I've worked with a bank at a fund management application and money is annoying in surprising ways. Some background: funds can handle fractional quotes and each

I've worked with a bank at a fund management application and money is annoying in surprising ways. Some background: funds can handle fractional quotes and each fund can have its own rounding rules, funds mixes can handle fractional percentages, when money enters or leaves the system it gets rounded to cents because you can't move fraction of cents (unless digital) So, you get issues even using arbitrary precision math. Operation order matters. Rounding impacts everywhere so you need to be consistent across the business logic, reversing an operation need to have rounding applied in a specific order to result in the final date to match the initial. Order is also important when splitting money, because the last share gets all the leftover cents that come from rounding the previous shares split so that the total gets allocated fully. I.e. moving the last 1$ from one fund mix to another mix that has 3 equally divided fund is going to round as .33 movement toward each, but you can't just leave that cent on the previous fund mix and you can't just drop it going nobody notices, so one of them gets .34