Amen. $2.13 is not enough!
But that's not the customer's problem. Take it up with the employer.
Do you know that. If the service was surly, inattentive, uncommunicative and ungracious, then $2.13 is too much.
My father had a formula - a large tip after an excellent meal with comparable service is the cheapest money you can spend if you intend to return. If everything was OK - not great but OK - then 15% on food and 10% on liquor (after factoring out any taxes).
I feel the same way - 20% when I'm happy and intend to come back.....for just OK, its 15%.