Way back when I was selling Auto Parts the favorite game the “bruthers” tried to play was to hand over a $20 or $50 bill for a $5 - $10 sale and then try to say that they gave Me a $100.
What they always failed to notice was that any cash I was handed got placed on the top of the cash register under a big bolt/nut until the transaction was completed.
They would try anyway and start throwing a temper tantrum when I showed them the money under the nut/bolt. Then they would leave bitching all the way out the door.
You must have worked in Memphis.
The only sensor related thing I can offer is that I apparently have a dead ambient air temperature sensor go bad this morning.
Yay....
learned to run a register the same way... and count the change back