Why is the displayed discount is different than what was entered?

Why is the discount shown on the receipt different from the actual entered value?

The deviation, which is usually no more than one to four cents, is that the discount on the individual items must be divided evenly.

Here is a small example:

You have three items on the receipt and give a receipt discount of $1, In this case, you can not split one dollar on 3 items: $1 / 3 = 0.333333…

This means that the cash, in this case, must be round, which results in only a 0.99 discount instead of a dollar.