How much do I tip the Balloon Pilot?

My statement comes from my wife's nail gal. She comes to our house to do her nails, we pay her the rate she wants, then my wife tips her as well. WTF? Its all cash. She used to work in a salon, but went out on her own. Wife still tips her like she was an employee on the salon. She owns her own nail business.....Mobile..
My comment to this is how does she keep her books, does the IRS assume she gets tips.
My brother had a cash business (no tips) and periodically throughout the year one or two of his receipt books would get "lost".


Alan