I'm amazed that so many kids don't know how to make change when they don't have a calculator handy. The item was $3.29. GST was at 5%. The poor kid was lost. I said, "The cost of the item is $3.29. Five percent of that is $.16. That's $3.45."
The kid was happy. S/he gave me a plaintive look that implored an answer. I said, "You have to give me $1.55."