>It's may be better than having to take both items home and wasting one,
???
How is taking both items home, possibly wasting one, better than taking one home, and taking the other in a few weeks and having no wastage? You're just hurting yourself (by possibly wasting an item) just to deny business some fraction of a cent worth of interest, which in ironic given that convenience stores are high margin businesses and you're choosing to buy from them in the first place. Whatever margin they made on the sale far exceeds any "interest-free loan" you gave them.
