Whenever you run across some mathematical function that has a name, a consistent meaning, and even a special set of symbols you should *know* that this function has a very widespread use.
There are all kinds of uses for ceiling, floor, and related concepts such as rounding. One example: Fractional pennies don't exist, yet a number of calculations will yield fractional pennies. What to do with those things? If you're being fair you'll try to round so that sometimes the customer wins, sometimes the seller wins, but on average, it comes out even. If you're not being fair, there are lots of nefarious salami slicing schemes that let those fractional pennies pile up (in your account of course) and eventually yield lots of dollars.