Practice this and these here.
Cashier dialog:
A: How much is this (singular noun)? How much are these (plural noun)?
B: It is $... They are $...
A: Fine. I will take it. Fine. I will take them.
B: How would you like to pay?
A: I'll pay cash. I'll charge it. I'll use my credit card. I'll write a check.
B: OK. Here is your receipt. What is your phone number for returns?