It's wrong to try to scam someone.
Tom is working as a server that depends on tips and is taking care of a large party as his customers.
Tom wants to get a large tip from the party.
Tom is gracious and helpful to his customers and thanks them when he gives them their check.
Tom decides to sneak in a larger percentage tip when the customer pays for their bill.
The customer appreciates how hard Tom worked while being their server and gives Tom a tip that is double the average amount.
The customer discovers the higher tip while viewing their bill and reports Tom to the manager, who then fires Tom.