How do u open a victor 515 cash register with out a key? -

Unusually there would be a latch at the back on the bottom and you need to slip string to pull it and it will open

Depends on which key you are talking about. If the on/off/x/z key then you can pop the drawer usually from a little latch underneath the register. If you mean the drawer lock key, then that is different. You need a locksmith, or you need to pry it open.