Answer to the puzzle

Adding the 27 cents that the kids paid to the 2 cents that the cashier pocketed is the wrong calculation to make. I tricked you into adding the wrong things. You're supposed to add up the money that "is." There's 25 cents in the cash register, 3 cents in the kids' pockets, and 2 cents in the cashier's pocket. That adds up correctly to 30 cents.