The short answer: if you are using the American Automobile Association, you do not need to tip.

We recently called AAA and asked a service representative about tipping for emergency roadside services such as replacing a flat tire, towing a car, or jumpstarting a battery.

"You don't need to tip," the representative told us.  Auto service personnel are paid for their work and tips do not make up part of their compensation.  "Tipping is not expected and it's a rare person who tips."

We were told that we can choose to tip if we want, perhaps for difficult circumstances or exceptional service.  Considering how quick and routine services have become, though, it's not surprising that tipping is uncommon.