That officer needs #1 TO BE FIRED for conduct unbecomming an LEO, #2 Charged with unlawful battery of a minor, #3 Stipped of his certification and barred from ANY law enforcement jobs in the future.
That was the most unprofessional behavior I have ever seen. First off, he should have double checked the denomination of the bill and he should have stated to her "OUT OF TWENTY"! When you do that, it clearly indicates you know what you are giving the cashier. The microphone would have picked up that. Regardless of that, he gave her a ten. There is no indication on the video that she pocketed the money. The officer should have asked the manager quietly to double check the register. If it came back short or over, then there is a problem. If not, the officer should have accepted the result as his mistake, apologised and left.
I would never want a guy like that working along side me!