If the customer is paying with cash, hit the plus key {+} then type in the amount of money you are given and hit {OK -ENTER}.

In the image below, the cashier has hit the {+} key, and the customer has given the cashier $250.00. 

Hitting {ENTER} or clicking "OK" in the pop-up box will complete the transaction and open the drawer. 

A yellow box will appear in the center of the screen. It lets you know the correct amount of change to give to the customer.


The change amount will also be listed in the bottom right hand corner of the screen.