U.S. stops minting pennies. What could it mean for shoppers and retailers?

The U.S. stopped minting pennies this week, and some groups have issued a warning about the headaches that can create for some businesses and consumers.

Retail business organizations said halting production of pennies could lead to a shortage that puts retailers in a pinch.

Rob Karr, president and CEO of the Illinois Retail Merchants Association, said the phasing out of the penny has been discussed for years, but now that it's reality, so too is the conundrum for retailers.

"If they have no pennies to hand out, they can't make change. So they have to make a decision; you know, rounding up or rounding down to that nearest nickel," he said.

Karr said the federal and state governments haven't set out guidance for what retailers should do, leaving them in limbo that could make them liable under consumer protection laws.

"Does all the rounding occur just on the tax, or is it a proportional rounding of both the product and the subtotal and the total that includes the tax? There's a whole lot of issues that have to be discussed," Karr said.

There's also concerns about those paying with a card.

While cash-paying customers could see totals rounded down to the nearest nickel, card-paying customers would pay the exact amount, prompting questions about uniform treatment.

"Then you have SNAP issues. So, SNAP recipients cannot be treated differently than non-SNAP recipients and vice-versa," Karr said.

Karr said lawmakers need to address these issues to avoid a wave of problems prompted by the penny being pulled from U.S. pockets.

"It's really just a game of trying to get these questions resolved before we reach a critical tipping point, which I think will come faster than everybody realizes," Karr said.

Karr says his group is already working with the Illinois Department of Revenue, as well as state and congressional lawmakers to work on guidelines for retailers.