[munch117]

The answer is accounting. In accounting you want predictability and reproducibility more than anything, and you are prepared to throw away precision on that alter.

If you're summing up the cost of items in a webshop, then you're in the domain of accounting. If the result appears to be off by a single cent because of a rounding subtlety, then you're in trouble, because even though no one should care about that single cent, it will give the appearance that you don't know what you're doing. Not to mention the trouble you could get in for computing taxes wrong.

If, on the other hand, you're doing financial forecasting or computing stock price targets, then you're not in the domain of accounting, and using floating point for money is just fine.

I'm guessing from your post that your finance people are more like the latter. I could be wrong though - accountants do tend to use Excel.

[jcranmer]

To get the right answers for accounting, all you have to do is pay attention to how you're doing rounding, which is no harder for floating-point than it is for fixed-point. Actually, it might be slightly easier for floating-point, since you're probably not as likely to skip over the part of the contract that tells you what the rounding rules you have to follow are.

[munch117]

Agreed. To do accounting, you need to employ some kind of discipline to ensure that you get rounding right. So many people erroneously believe that such a discipline has to be based on fixed point or decimal floating point numbers. But binary floating point can work just fine.