The woman, known only as Anne-Marie, works for a branch of the Cora supermarket chain in Mondelange in the eastern Moselle area of the country.
Local newspaper Le Républicain Lorrain reported that the cashier noticed a promotional offer for a fast-food restaurant on the back of a receipt left behind by a customer. She took the receipt, thinking she could treat her son with the "2-for-1" promotion.
"I was thinking about my eight-year-old son," she told radio station France Inter. "I tore it off, honestly in front of everyone and then just afterwards, at around 2pm at the end of my shift I was summoned to the see the head of security and my boss who said it was the property of Cora."
Anne-Marie has worked for the supermarket for ten years and earns €940 a month ($1,320). She is also a representative for the CGT union.
Shortly after news of her story was reported an internet campaign sprang up in her defence. Twitter users sent messages of support while the company's Facebook page received thousands of comments. Some speculated that the reason for her dismissal could be her role in the union.
In a hasty U-turn, Cora announced the woman would no longer face dismissal.
"The management of Cora Mondelange has decided not to pursue the case against an employee. We are aware of the emotion generated by the news that appeared this morning," the company said on its Facebook page.
Twitter users were quick to congratulate themselves on their mass action.
"Bravo Cora, which managed to make an offer for one euro off a hamburger worth bad buzz of one million euros" wrote Maitre_Eolas.
"The Cora affair: how social networks can sometimes be useful" wrote vainsylv.