Police said the bandit approached a clerk at the soda machine in the Hempstead Avenue store, showed a handgun and told her to put money from the cash and Lotto registers into a gray gym bag.
The man also demanded access to the store's safe, but the clerk said only the manager could open it.
No one was hurt.
The man fled and was last seen on foot turning left onto Lindberg Street.
Police said the suspect is described as thin, about 6 feet 2 inches tall, clean-shaven, with dark skin and crooked teeth. He was wearing dark blue jeans and a gray hoodie.
Detectives ask that anyone with information about the robbery to contact Crime Stoppers at 1-800-244-TIPS. All call will be kept confidential.