Charlotte, N.C. ? Bank of America Corp., one of the nation’s biggest financial institutions, has unveiled a plan to make it easier – and potentially more rewarding – to start putting money aside.

The service, dubbed “Keep the Change,” allows customers to round up their debit card purchases to the nearest dollar and have the difference automatically transferred from their checking account into an interest-earning savings account at the end of the day.

For example, a debit card purchase of a sandwich and drink for $5.45 would be increased to $6, with the extra 55 cents going into the customer’s savings account.

To drum up interest in the program, the bank will match all contributions to the savings account for the first three months. After that, the bank will match 5 percent of the total. The matching funds would be credited annually.

“Our customers have told us they’re not saving the way they wish they were,” said Diane Morais, senior vice president of deposits and debit products. “We designed a very simple way to do it with what they do every day.”

Still, the proposal was met warily by a consumer advocate.

“They are trying to increase the use of debit cards to increase their profits,” said Ed Mierzwinski, consumer program director for Washington, D.C.-based U.S. Public Interest Research Group.

Bank of America stands to profit by earning a fee for each transaction made with debit cards. Banks typically charge merchants 1 percent to 2 percent of the purchase price for each debit card deal.

Mierzwinski said the bank was using the program to encourage more small purchases with the debit card, which could lead to higher prices for items ordinarily purchased with cash.

“If so, everyone will pay more for that cup of coffee because the stores will need to increase the price of their goods to overcome the fee increase,” he said.

Bank of America spokeswoman Tara Burke declined to comment Tuesday on Mierzwinski’s claim.

The bank has an annual cap of $250 for “Keep the Change” deposits. And the bank requires a minimum balance of $100 for a customer to obtain the service.

“We anticipate the average customer can save between $150 to $200 a year through this service,” Morais said.