When customers buy dresses or shoes at Sandpiper, Melissa Murdock's Vinings boutique, she tries not to think about just how much money goes to the banks and credit unions that issue debit cards her customers swipe.

"I don't look at it because it makes me sick to my stomach," Murdock said. "It's thousands of dollars a year."

Bankers say the charges for debit card swipes -- called interchange fees -- are the cost of maintaining a network that allows customers the convenience of cashless transactions. Retailers say the prices have been rising on their backs, and it's time for a change.

And while July 21 marks the expected switch in fees from a percent-per-swipe to a flat rate for each debit card use, thanks to an amendment passed last year, several bills introduced in the U.S. House and Senate are proposing that the switch be delayed so the effects of the new law can be studied longer.

There is no way to know, now, whether the law will go into effect as planned, but retailers say relief cannot come soon enough.

Murdock, whose average customer spends $480 at her store, said she pays between 2 and 7 percent of each transaction to the debit card issuers. On the low end, that's $9.60 for an average sale. On average, retailers are paying 44 cents per swipe.

The new rules would allow charges of 7 cents per swipe, with the possibility of charges as high as 12 cents per swipe depending on the cost to maintain a particular system.

With the potential savings, retailers will be able to hire new associates, lower their prices or offer other customer benefits, said J. Craig Shearman, vice president of government affairs for the National Retail Federation.

For retailers that have been hanging on "by the skin of their teeth," the potential for change has been a long time coming, said John Heavener, president of the Georgia Retail Association.

"Swipe fees can completely leave a retailer in the hole," he said. "They can start to have a little breathing room."

Murdock said she would use any funds to pay down debt she accumulated during the recession, for marketing, and perhaps for a vacation. But she said she expects banks to find other ways to recoup the money lost.

SunTrust Banks does not yet know what it will do to replace that income if the law goes forward as planned, but the bank will no longer offer rewards for using a debit card, beginning next month.

Spokesman Hugh Suhr said in an e-mail that the Atlanta-based bank brought in $332 million in interchange fees in 2010. If the law goes into effect for the second half of the year, SunTrust could see a 75 percent reduction in fees during that period.

Nationwide, banks could lose $12 billion in revenue, said Joe Brannen, president and CEO of the Georgia Bankers Association. He disputed the idea that savings would be passed on to customers and said retailers benefit from the fraud protection and immediate availability of funds that they get with debit cards.

"There are enormous benefits. They just don't want to pay for it," Brannen said.

Brannen also said since the regulations allow banks with less than $10 billion in assets to operate under the old rules, retailers would be able to discriminate against smaller banks and credit unions, whose interchange fees would cost them more.

That isn't the case, said Dwaine Kimmet, Home Depot's treasurer and vice president of financial services, since retailers who accept one card with a MasterCard or Visa logo are required to accept them all.

Kimmet said over the past four years, Home Depot’s PIN debit interchange fees have risen by 50 percent, and are the third-largest cost for the company, behind occupancy and employee wages. About 20 percent of all sales are made with debit cards.

If the law goes into effect as planned, Kimmet expects Home Depot to see a $35 million reduction in costs. The company would use the money to reduce prices, hire associates or extend the length of deferred-interest credit card offers, he said.