Money Making Envelope (Three times)

How poss A magician shows a 5 yuan bill which is wrapped by 3 pieces of papers.
He wrapped it again as it was before, and unwrapped it again. 
Magically the bill inside the paper bag turns to a 10 yuan bill. 
He continues to repeat the actions. 
10 yuan bill turns to 20 yuan bill and at last 20 yuan bill goes to 100 yuan bill !?
How possible?   But he did! under your watching eyes!