Another receipt problem

Some time after the Russian idiot (see post below), I drove a "normal" person -- a businessman. He went from a nice hotel to the Marriott Coronado. The fare was $19, and he asked for a receipt written for $33. I wrote out the receipt, with the amount blank, as he placed $30 on the arm rest. I handed him the receipt.

Him: I need you to fill in the amount, $33.

Me: You only gave me $30.

Him: The receipt is for work. (He's going to defraud his employer.)

Me: Do you want change back?

Him: Yes, $10.

Me: You're going to give me $1 extra, while you get $13 extra? Why don't we each take $7?

Him, agitated: Just put in $33.

I put in $5, with a line before and after the numeral. I gave him $11 back (no tip), and he got out in a huff. What a dumbass. If I'm going to join a conspiracy, even a small one, I need to get something out of it.