If Indiana Sales Tax is 6% and a breakfast meal at McDonald's is advertised for $3.10, why did it end up costing me $3.87? (with tax should have been about $3.29). Are they allowed to add in other taxes?

Based on the amount, it sounds like the cashier rang up the components of your meal without recording it as a combo, which discounts the purchase ('meal deal').

Any deviation from the stated combo meal, however, will add to the price (add cheese to a sandwich that doesn't automatically come with it, a hash brown, or upgrade from a small coffee or OJ to say a medium pop). I doubt it was additional taxes, just error.

  It looks to me like you got overcharged to the tune of 58¢.  Is it possible that you ordered an additional item, not covered in the original $3.10?  With tax, an additional 55¢ item would take you to the total that you ended up paying.  If not, then yes, you were definitely overcharged.

From what I can figure out about this is; restaurants charge a higher tax because the provide a Service.
In Maine where I live, the sales tax is 5%, but restaurants and even convienance stores charge 7%.
Just another rip off to the consumer.

It's probably a restaurant tax. We have them here in VA, and they are more than the sales tax. It's 10% on any food item.

mayb there are other taxes you don't know about yet... or they simply make it cost more so thy can have more money...

They are charging now for sauce packets. Did you want BBQ or Sweet & Sour Sauce for your breakfast?

Sales tax in Indiana is 7%. If you made your purchase within the Indianapolis metropolitan area you were probably accessed the Lucas Oil Stadium & Conseco Fieldhouse construction (extortion) taxes as well bringing you to 9%. Even then it sounds as if you were overcharged. Restaurants often over charge people.

There are counties in Indiana with local taxes. Particularly the Metro-Indianpolis area, which has additional taxes that originally went to pay for the "Hoosier Dome" and that are now going to pay for whatever new football stadium they decide to build.