The incident happened at the McColls store in Hirst Gate, Mexborough, at around 9.30pm on Wednesday December 28.
After stealing cash, the man left the store and drove off in a white Ford Transit van, thought to have been parked nearby.
Officers are keen to speak to the man in the CCTV image in connection with the incident.
Anyone with information is asked to call 101 or email [email protected] quoting incident number 988 of 28 December 2016.
Sheffield sexual assault: Girl, 13, victim of 'serious' sexual assault in Chapeltown
RSPCA: 9 cats and dogs looking for a new home this month at Sheffield's RSPCA branch
Water Slacks: No arrests made during armed police raid in Sheffield neighbourhood
Caught on camera in Sheffield: 10 people police want to speak to in connection with criminal investigations
Power cut Sheffield: Hundreds of homes in Hillfoot area without power ahead of 28C heatwave today
Information can also be passed to Crimestoppers anonymously on 0800 555111.