I just saw in this week's Dollar General store circular that they are offering 10% off Nintendo eShop and GameStop gift cards this week from 6/9 to 6/15. The ad shows the $20 Nintendo eShop card and the variable amount GameStop card ($20 to $500) along with a Domino's card in the picture.
Underneath, it also shows a deal where you can save $5 by buying two $25 PSN cards. There are also Applebee's, Cracker Barrel, and Taco Bell cards in the same photo where you can mix and match them with the PSN cards. The disclaimer in the photo says it excludes the $10 PSN cards, and it's one discount per customer on the PSN cards.
Waiting for the obligatory "only 10%, that's not a good deal" and "they can't keep me from going into the store multiple times to get the PSN discount" posts.
Also, in the past, Dollar General stores have been notorious about denying gift card purchases with credit cards, so I would recommend using debit cards or cash to make these purchases.
That is all.