The theft happened at the store on Swinton Hall Road sometime between 11.30am and 12.10pm on Tuesday 23 June.
The offender is described as a white man with long, collar-length hair, of a medium to large build and wearing a black jacket and white trainers.
Police are now appealing for any witnesses who may have been shopping at the time to get in touch.
Anyone with any information can phone Crimestoppers anonymously on 0800 555 111 or Swinton Neighbourhood Policing team on 0161 856 5228 quoting reference number 230615/0853.