Whataburger review: Poor customer & cheating

On the morning of Dec 5th, I went thru Whataburger drive-thru and ordered a biscuit & gravy and a small coke. The cashier charged me $4.81. I gave him $10.01 to cut down on the pennies in my cup holder. He gave me back $5.19. As I was looking crazy at the change in my hand the cashier asked me what was wrong. I asked him if I gave him $10.01 and he said yes and I informed he should've given me back $5.20. He left the window and I was sure he went to tell the cook to spit in my food. He asked for the change he gave me and returned 20 cent in silver which he should've done initially. I apologized and proceeded to the pick-up window and was handed my order. I noticed potato sticks in my bag and informed the attendant this may not be my order. He said you ordered a biscuit & gravy 'meal'? I said, 'no, it should've been just a biscuit and gravy', so the attendant called the manager who walked up and said that's the lady who got mad about a penny. I heard him and said 'I didn't get mad about a penny but I'm getting mad now. Just give me a refund' (because now I definitely know they would spit in my food)! The manager gave me a refund. But as I drove off, I should've mentioned that not only does the cashier get orders wrong, he can't add or subtract and I'm sure he had been cheating people out of money as long as he had to figure it out in his head.