Detective Inspector Kevin Burke said officers were still trying to determine what weapon was used by three people to smash the front glass door which was usually locked at night.
After grabbing the till and cigarettes, he said the three left on foot to the driveway of a football club opposite the service station and left in a yet-to-be-identified getaway vehicle.
Yesterday's robbery was the fifth at business premises in Whangarei since March 5.
The other four happened at Maunu Four Square, Maunu Superette, Otaika Four Square and Liquor Land in Otaika.
Mr Burke said police patrols around retail outlets, which started after a spate of aggravated robberies of dairies and liquor stores, would continue.
"We are also asking people to be vigilant, even when they are travelling at night. If they see something suspicious but which they may not think is important, they should ring us," he said.
BP spokeswoman Anna Radich said company staff were well trained to handle situations such as a robbery or security breaches at its stores.
She said the male employee during yesterday's robbery did a fantastic job by following the correct procedure to ensure his safety.
BP would now undertake a thorough review of its safety and security procedures, she said.
"Our after hours staff wear alarms which immediately notify security services when pressed. Staff are encouraged to activate their alarm at any point if they feel like they are in danger," Ms Radich said.
As well as working closely with police, she said BP staff also participated in safety forums that are designed to facilitate information sharing and safety learning among other retailers in the country.
"This enables us to discuss trends, pinpoint high risk locations and share best practice with each other in the interest of safety," Ms Radich said.
Anyone with information about yesterday's robbery is asked to contact Whangarei Police Station on 09 4304500 or Crimestoppers anonymously on 0800 555 111.
