A three-strong gang, armed with weapons including a gun, struck at the Parkway Drive store, Darnall, at 4.40pm, yesterday.
Video footage of the aftermath of the incident captured the masked men running away from the store and leaving in a blue car.
South Yorkshire Police said nobody was injured in the raid.
It has not yet been revealed what was stolen.
Posting on Facebook, witness Amy Hewitt claimed on of the robbers was armed with a hammer and tried to steal jewellery form the store.
She said: “They were trying to get the jewellery one of them had a hammer trying to smash the glass cabinet.
“Not the best experience I’ve ever had.”
Anyone with any information should call South Yorkshire Police on 101 and quote incident 622 of April 28.
Crimestoppers can be contacted, anonymously, on 0800 555 111.