Question

A customer buys an apple pie for $8.04, 6 cloves of garlic for $0./9 each, and a quarts of milk for $1.31. You are working the cash register. The customer gives you a $5 bill, six $1 bills, and a quarter. The register tells you that you ow the customer $0.16 . Round the price of each item to the nearest $0.10 to estimate how much the customer owes.

Answer 1

Round 0.30 each (or $1.80 for all 6 of them), the milk is $1.30. Total of estimates is $11.10
 
 The customer gave you 5 + 6 + 0.25 or $11.25, which is very close (and slightly higher) than the total of your estimates. I'd guess the register is correct.
 
Actual value is $8.04 + 6*0.29 + 1.31 = 8.04 + 1.74 + 1.31 = $11.09. The register is definitely correct.