Hmmm. I should search the cash register for hidden keys.
The cash register is probably a good place where to hide some spare key.
It is an old electronic cash register. As you might expect, the drawer is closed. In this particular model it can be opened in two ways: either by means of a physical key, or by entering a numeric password on the keyboard.
Oh, and of course you can try to pick the lock, but you would need some tool.