We don't have fast hardware decimals, except on IBM mainframes. So, if you need fast financial calculations which are too complicated for integers (e.g. gasp division), you usually use decimally-normalized doubles and do it very very carefully.
This is a sad state of affairs, but nobody was fixing this in the last 30 years, so there's that.
This is a sad state of affairs, but nobody was fixing this in the last 30 years, so there's that.