another mystery

Today I got my car washed at one of those full service places that we all have around. It was $11, but, the automatic touchless deal in town, "Mayberry Water WorkS", is $8 and doesnt really do a good job. I got a vacuum too.

After my car had gotten the pre-wash scrub, it went through the carwash and then came out the other end to be dried and detailed by a person. The young lady pulled the car forward and dried it, sprayed and cleaned the windows, and then detailed the wheels. She appeared to be doing a good job, but, how much should I tip her??? (sometimes its a him)

When I got home, I realized she had not done that great of a job, but the tip was in. $4 is what I gave, what do you give???