The staff here, or maybe it is the cash registers, are not exactly reliable. Be prepared to consistently be over-charged or under-charged. Also, if you special-order your food, you probably won't get it the way that you want it. For instance, "no onions" will get you onions on your burger 6 out of 10 times.
Even though the ordering process isn't flawless, the burgers are still darned tasty.