Police say that just before 2 p.m., the robber entered The Barn on Little East Neck Road in West Babylon and demanded money from the clerk.
He then managed to get away with an unknown amount of money.
According to investigators, the suspect fits the description of a man they're looking for in connection with a robbery spree over the last two months.
They believe he's responsible for nine other machete and knifepoint robberies of businesses, including several Carvel and Subway franchises, that span Nassau and Suffolk Counties.
The most recent robbery happened on April 8th when the suspect held up a Subway restaurant in Westbury.
No one was injured during Tuesday's robbery.
The investigation is ongoing.