In Need Of Humble Pi

Me: “Would you like to donate to [charity] today?”

Customer: “Okay. Round my total up to $30.”

(I pull out a calculator to figure out how much it is to round up to $30. Customer’s total is $25.78.)

Customer: “It’s sad that you need a calculator to figure that out. It’s $7.32.”

Me: “Actually, ma’am, it’s $4.22.”

Customer: “Oh.”