We have small cards, red one side green the other, which hang over the screen. red= dirty till, green = clean till. If the till is not green then we refuse to use it as a multiskiller.
I was asked to hop on a red till one day by duty and refused until it was cleaned. Duty decided to make a fuss about this, they only wanted 1-2 customers let away to help, but it ended with the store manager agreeing, saying I was right to expect the till to be clean.
If we do hop on a green till then when we open the drawer find it is not clean we are allowed to immediately request it be cleaned and have it noted as such, in case there is a problem, but that has never happened me, the TL's do their job correctly and tills are always green....