The robbery happened on Sunday at the Somerset Deli-Grocery on North 9th Street.
The suspect, who had a t-shirt wrapped around his head, rushed the counter and demanded cash.
After taking handfuls of money from the register, he took off.
There were no injuries.
The suspect is described as a black male in his 30s with a medium build. Along with the white t-shirt around his face, he was wearing black t-shirt, black pants and black shoes with white soles.
He also had tattoos on his right forearm.