Where's Count von Count when you need him?

I always though that counting money was absolute not relative...

There is this diner near us that has some decent food and reasonable prices. There are several locations all independently owned but Don Coupon is partial towards one particular location. So imagine my happiness when on the back of my supermarket receipt there is a coupon for either Buy one sandwich/burger and 2 drinks and get one free OR 20% off.

Sounds simple right?

Well so we head to the counter and  order 2 sandwiches and 2 drinks. Presented the coupon. Was told we could not use the sandwich coupon because one of the sandwiches was "on sale". Now this I take an issue to. The prices on the board are the SAME as they have been for years. This does not a sale make. It simply means they are FOR sale not ON sale. Was told we could use the 20% of your entire order coupon. OK fine whatever still a good deal.

When I got home to look at the receipt I noticed that on the line item where it said 20% of it took 74 cents off. On a $20+ ticket. On what planet is 74c 20% off your entire order. Not mine! It looks as though we got 20% off the drinks only. 

What to do, what to do. Complaining to the manager/owner is useless since he was standing right behind the cashier the whole time. It really does seem like they want the benefit of having customers come into the store but don't want to yield the discounts promised. I really DO feel like filing a complaint with the L.A County Department of Weights and Measures on this issue....