so the keyboard input can clearly show the currency that is entered. This can be very important in multi-currency applications, e.g. travel (both customer and admin).
That actually sounds like an idea whose time has definitely come. Anyone here on the HTML standards body (or works for Google in the requisite part of the Chrome team)?
There are other uses for fixed precision besides currency (co-ordinates, tolerances, etc.), but currency would be used a LOT!