Should you tip the people that bring you your food at the Sonic fast food chains?

I have my own rule for this. The only time I tip is if I am eating. I do not tip if I just get any of the following.. drinks, ice cream, a side like tots.. If I get an actual combo meal then I will give a dollar or the change. I have gone and just gotten a drink and I have had the car hop take my 2.00 when I think the total was like 1.10 or so, and she smiled and said "Thank You" as she turned around and kept the change. I was blown away... I never tipped her nor did I indicate that she could keep the change!! I DO think they make you feel as though you have to tip, and some even give you a look when you don't.. I just had my daughter, and when I was pregnant I would totally crave BLTs from sonic. Even though they were just like a dollar I could not afford to tip each time. I did not work while I was pregnant, and since it was such a cheap item (and umm some days I might have gone 2-3xs) I did not tip. I can't say I see the point in tipping where if you gave a dollar it would almost be the total of you order.. Now if I am just running through I go to the drive thru for that reason exactly!.. ** Let me just say that when they are packed like when they have free root beer float night, I do give them something. Afterall if something is free it is only right to give them something even if it is a quarter..