Tens and a Five Wikipedia
Tens and a Five is a variant of the shortchange scam. The con artist hands the mark, usually a bank teller or cashier, a $20 bill (or equivalent in other currencies), and asks for "tens and a five". The con artist will then start a lengthy conversation to keep the mark's mind busy. It is hoped that the mark will, in a state of confusion, hand over two $10 bills and a $5 bill, due to the misdirected language.