SLPT: Any cash money given to you when you work a cash register is your money! It was handed over to you! You get to decide how much to keep and how much to give to the business.
End of shift till balance? Nope, the till is sitting squarely on the counter and not balancing on anything.
This also applies to the customer wanting "change". Screw you, buddy! You handed me the money. No takesies backsies.