>We can solve these problems by rounding after every operation. In my experience one should do exactly the opposite, round/format only the very last result whe

>We can solve these problems by rounding after every operation. In my experience one should do exactly the opposite, round/format only the very last result when you need to print it, otherwise always keep all the decimals in the intermediary results to avoid accumulating rounding errors as in a Superman 3 bank hack (aka "salami slicing"). I did a lot of affiliate and e-commerce software in my time and if you're careful you can use floats (sometimes you have to deal with old systems working that way), but fixed-point calculations with integers are way easier and safer. Just make sure to store enough extra decimal places, not just the 2 that you print and you can calculate interests, exchange currencies, charge 0.5% fee on $0.01 per click transactions, whatever - it works just fine.