Dear Counter-Guy At The Wiz Who Checks Customers' Receipts Before Handing Them Bags In Which To Place Their Purchases:
A "thank you" would be nice. A simple "thank you". That's all. You don't have to wish me a nice day or a nice Memorial Day or a nice life or a nice anything. All you have to do, after I've showed you the receipt for my purchase, is part with a bag and the words "Thank you." I'd even accept a mere "Thanks" if you're not feeling up to the task of offering two words.
If you want to add, "Oh, and thank you for patronizing this store, because without our customers this place would go out of business and then I'd be out on the street looking for another job where I can be a surly, sullen-faced zombie," that would be fine too.
Someone Who Thanked You For Nothing and Who Will Take Her Business Elsewhere From Now On, You Jackass