The presiding judges said the infraction by Barbara E., known throughout Germany by her nickname Emmely, was not worthy of termination because the value of the deposit slips was so low.
The cashier's employer had contended that 52-year-old had irreparably destroyed its trust in her, however, the labour court said her long service should have counted for more. Emmely claims she was singled out by Kaiser's for her trade union activities.
"I'm overwhelmed," she said, adding her greatest victory would be to return to the checkout counter where she had worked for so long.
Kaiser's lawyer, however, said it was unclear if she would get her old position back.
"I can't comprehend the justification," said Karin Schindler-Abbes.
The court decision on Thursday is the latest chapter in a high-profile legal battle between Emmely and the supermarket chain starting in August 2008. The saga sparked outrage across Germany, as the cashier's supporters feel she was unnecessarily persecuted for a minor offence.
In recent years, there have been several other cases involving Germans fired for misdeeds such as improperly eating leftover company food while on the job.
A disabled Hannover woman working at a nursing home was sacked after 18 years on the job for eating pâté intended for patients last November and in October a court in Baden-Württemberg ruled that a 58-year-old nursing home worker was rightfully sacked for taking home leftover Maultaschen, a Swabian specialty similar to ravioli.
Those incidents were preceded by a 59-year-old Dortmund secretary who was fired after 34 years on the job for snagging a Frikadelle, or meatball, after setting a conference buffet for her employer, the North Rhine-Westphalian building association. The company later retracted her dismissal in response to public outrage.