Of course, it is useless to ask children "why, how". He may not even know why he did it. If you insist on asking him to answer "why", all you can get may be another lie. At this point, the best way is to show that you are willing to discuss with him that he needs money:
"I'm disappointed that you didn't even tell me you needed ten dollars."
"When you need money, be sure to tell me. Things can always be discussed. "
In short, parents should never force their children to lie when they discover their "bad" behavior. In this way, it will undoubtedly hurt our already hurt feelings again. When exhorting children, the art we should master is: "If we already know the answer, we will never ask questions again." We just need to make a public statement. The result of this statement will be just right: what is given to the child is the unhappiness he brings to himself and the punishment for taking responsibility for his bad behavior.