How to make a cashier laugh

Today at the store I purchased two candy bars and a water bottle. The cashier rang up my total and said "Your total today comes to $28.98" I looked at him and said Not today Satan, the devil is a liar. He laughed, looked at the register and apologized for his mistake. He apparently forgot to clear the price check he did a few minutes prior to me walking up. As I collected my things, he thanked me for his laugh. As I walked away, I could hear him saying "not today satan, the devil is a liar" LOL!!!