It happened on January 17 inside the Red Sun Food Mart on the 2200 block of South 12th Street.
The suspect was captured on surveillance walking into the store at 7:15 p.m.
He grabs a soda and puts it on the counter to purchase.
VIDEO: Click here to watch the surveillance video
When the cashier turns her back, he walks behind the counter and grabs the entire cash register.
He carries the register out of the store onto the 1200 block of Daly Street where he was then seen forcing it open and stealing the money from inside.
Police describe the suspect as a white male, 35 years-old, 5'9" tall and 225 lbs. He was wearing a light blue hooded nylon jacket with gray interior, dark blue hooded sweatshirt with white paint or spackle, dark baseball cap, blue jeans with white paint or spackle, and tan boots or sneakers.
Anyone with information is asked to contact police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).
All tips will remain confidential.