"Police will not tolerate any threats of this nature towards members of our community," he said."
"Based on the continuous information provided to us by the public, neither will our local residents. These arrests are significant for providing reassurance to the victims and preventing further serious incidents of this nature."
He said the four teenagers were due to appear in the Levin Youth Court on Tuesday 12 September, and the woman would appear in Levin Court on the same day.
The dairy's owner Ella, who did not want her surname published, said the robbery, in July, was very scary.
Despite the shock of seeing three masked offenders approach her while she was alone in the store, she managed to remain calm, push a panic button and escape into the back room of the shop.
"I looked at the gun, and thought - is it a toy? But it looked real so I pushed the panic button and ran out back," she said.
"You don't want to fight them if they have a gun."
She believed the offenders were locals, and was concerned about the increase in crime related to the increased price of cigarettes and tobacco.
Ella said the offenders had come prepared to take cigarettes, bringing an empty washing basket, which they filled with the more expensive brands.
Detective Sergeant Skogland said the store's staff members were receiving ongoing support.