The car was last seen driving off at speed, almost colliding with a truck in Prince Ave in the direction of Papamoa and possibly along Maunganui Rd.
The victim, who spoke to the Bay of Plenty Times on the condition she was not named, said: "I've been in retail for 25 years and there have been other incidents, but this is the first time I have had a knife pulled on me.
"It wasn't a pleasant experience, but luckily no one was hurt. I'm sure police will catch-up with the offender soon with the public's help."
Detective Sergeant Alan Kingsbury said the offender may have also entered other stores canvassing potential places to rob, prior to the robbery.
Mr Kingsbury said police were patrolling in the area yesterday talking to storekeepers and businesses, and also still investigating whether there was any CCTV footage.
Police want to hear from anyone with any information, particularly people working in the area at the time of the robbery, he said.
"No matter how small, unusual or inconsequential people think it might be, somebody in the community has a piece of information which is the key to solving this crime," he said.