Most things in front office use floats in my experience, e.g. derivative pricing, discounting, even compound interest. None of these things are going to be any better with integers or fixed-precision, but maybe harder to write and slower.
Yes, the risk management/instrument pricing part in the "Front Office" uses floats, because the calculations involve compound interest and discount rates.
And the downstream parts for trade confirmation ("Middle Office"), settlement and accounting ("Back Office") used fixed precision. Because they are fundamentally accounting, which involves adding things up and cross-checking totals.
These two parts have a very clear boundary, with strictly defined rounding rules when the floating point risk/trading values get turned into fixed point accounting values.
