The Citizens Crime Commission has offered a $5,000 reward for the arrest and conviction of the suspect.
The incident happened around 2:50 a.m. on the 5000 block of City Avenue.
Police say a female clerk was stocking shelves when she noticed a man at the register.
The clerk walked to the register when the man stated, "Give me all the money in the drawer."
He then lifted up his shirt and revealed a handgun in the waste of his jeans.
The suspect fled with $90.
The employee was not hurt.
The suspect is described as a black male in his 20's, clean shaven, around 6 foot tall, 180 lbs, wearing jeans, black jacket and black knit hat.
Anyone with information is asked to contact Philadelphia Police.
