It happened just after 8pm on Thursday when a group of men threatened a member of staff as they were closing the store on Bawtry Road.
It is believed there were around six or seven people in the group.
Three were in black clothing, two had a face-warmer covering part of their face with a skull design, and the other was wearing a balaclava and sunglasses. All were around 6ft tall.
The member of staff was not physically injured.
Police are appealing for anyone who noticed the disturbance or saw suspicious activity in the area of Bawtry Road Industrial Estate and Staynor Hall to come forward.
Call 101 or Crimestoppers on 0800 555 111.