I don't think we have a definite answer for this, but I don't think buying new gift cards with reseller gift cards would make them "clean." Target can follow the path gift cards take, so if your cards are "unclean," I don't think conversion to a new gift card would cleanse them.
I would suggest that you check your eBay account to see if you have the 4x eBay bucks offer. You would have received an email and/or there would be a banner at the top of your eBay home page. As
@PerfessorZ has adeptly pointed out, your most "safe" savings may come from buying Target cards during an eBay bucks promo, as they would then be "clean," and you'd get a "discount" in the form of eBay bucks.
[This "clean/unclean" sounds so religious. A cult of Disney gift cards.]