If you ever opted for “cash-back” on a debit purchase at a Dollar General or Dollar Tree store, you might have been charged an unnecessary fee. According to findings from the Consumer Financial Protection Bureau (CFPB), the brands – along with Kroger grocery stores – collect over $90 million in fees annually when customers request to access their cash.

“[These] three major firms charge cash-back fees even though other competitors offer it for free,” the CFPB noted in a recent report.

According to the CFPB’s findings, cash-back fees for small withdrawal amounts are the highest at the dollar store corporations — $1 or more for amounts under $50 — while at Kroger, the country’s largest grocery chain, customers are being charged $.75 for $100 or less.

And while all merchants are charged a fee for debit card cash-back transactions — between 5 cents and 20 cents depending on the transaction amount — Dollar Tree, Dollar General and Kroger are the only companies in the sample passing the charge onto consumers.

“All retailers in our sample offer cash-back services, but only Dollar General, Dollar Tree Inc., and Kroger Co. brands charge a fee,” the CFPB said, noting that Walmart, Target, CVS, and Walgreens offer the service for free. “Other retailers offer cash-back for free, even for withdrawal amounts similar to or larger than those provided by the three retailers who charge.”

And the CFPB said to charge for such cash access is exploitative.

“While the use of digital payment methods is on the rise, cash accessibility remains a critical component of a resilient financial infrastructure and dynamic economy,” the report concluded. “In this context, we observe that some retailers provide cash back as a helpful service to their customers, while other retailers may be exploiting these conditions by charging fees to their consumers for accessing their cash.”

But the Dollar Tree brand says the fee is warranted.

“Like many retailers, Dollar Tree and Family Dollar offer cash back as a convenient service for our customers,” a company spokesperson noted in a statement. “Shoppers who want to take advantage of our cash back offering are charged a clearly disclosed fee, which in turn helps offset the variety of costs we incur to offer this helpful service.”