Shorting a Cashier a penny or 2: Whats the limit

[mrkilla]

Whats an accetable amount of change you can short a cashier when making a purchase?

Lets say for example you go to your favorite Deli or store to buy a blunt and a 40 the total is 4.23 and you have 4.20 (you have other money if you wanted to break it you are not in dire straits here thats not the idea here )

Lets also included the "Give a Penn/Take a Penny" Trays I am curious whats the threshold on the Take.