Yeah, if you know your domain and know you're creating only an acceptable amount of error, by all means float it up. Floats are easy to use and predictable nearly everywhere, since nearly everyone follows the same spec.

Generally though, I think people don't quite do due-diligence here. And/or the domain changes enough that numbers get large enough to invalidate the earlier analysis. There are obviously exceptions to this though, and for them, they know what they're doing and why they're doing it and it's all good.