Money Laundering

I saw this happening at a  Walmart store the other day, 

The woman standing in front of me in the checkout line offered a 100 dollar bill in payment for her groceries. The clerk called the store manager. He appeared, looked at the bill, and told the clerk to give her the change, and walked off with the bill. 

What was going on here? Money laundering. 

A nicely dressed man had shown up at the woman's house, and gave her the 100 dollar bill, and told her to buy groceries with it at a Walmart store. That she did and drove off with a lot of groceries. The nice man showed up again and asked her for the change.

What happened at Walmart? All the 100 dollar bills were sent to a special location, where they were mixed with all the other bills that came in every day. 

Somehow, and I have no idea how, all that dirty money was replaced with clean money.

What happened next? A Bank examiner shows up and asks for the books. He looks at them, and sends a report "Walmart is doing some money laundering." and Walmart gets fined. 

Walmart complains to its bank, who notifies its representative in Washington. There are many of these, and they are strictly legal. They give the government a list of the companies they represent. And what they want in return is fewer bank examiners.