The IDs have a return amount limit for a reason, so don't feel bad about giving the guests store credit. Usually, the best thing you can do, is do the return, document it, and tell AP. Feel free to scrutinize their ID too. It must be valid. If it's expired, I don't take it. I also don't take photocopies of IDs either, or DMV papers. (No clue what the actual policy is.) But I only accept real, original, non expired ID.
There have been times where I cut the guest off at $50, and told them they were over their ID return limit. I've only done that when the guest had an absurd amount of items.
If it's HBA, I don't even take them. If it looks like it's over $30~, or coupon items, or small expensive items that are easy to pocket, I tell them I need an original receipt. No ID, no card look up, no gift card. Original receipt only. Same typically applies to electronics as well.
With electronics though, I usually attempt the return anyway, because over a certain amount, they have to do an exchange anyway. Same goes for baby formula.
One time a guest came in with two stuffed duffle bags, full of random merchandise. He wanted to return all of it, as well as the bags. I didn't even ask for ID, I flat out denied the return.
Just remember...you want to trust the guests. Never accuse. But, sadly, people do shady shit all the time. Just partner up with AP, keep a mental list of things for them, keep them up to date on what's been going on. Eventually you'll learn what to deny, and what to accept.