Mr Johnston said it was "perfectly legitimate" for people to defend themselves as the superette staff had, but police didn't recommend it.
"Our advice is it's only property, it's not worth risking an arm, or worse, to a meat cleaver," he said.
CCTV footage showed just how close the weapon had been to one employee's arm.
He urged anyone who recognised the youths, or had seen them "hanging around town," to call the Kaikohe station on (09) 405-2960, or Crimestoppers, anonymously, on 0800 555-111. They had disguised themselves but he was confident that someone would know who they were.
They had been "hopping around so much" that some had lost their bandannas, exposing their faces to the security cameras.
"We're hoping someone will be able to identify them before they hurt themselves or someone else," Mr Johnston added.
Hemant Patel, who owns the superette with his brother, said the incident had been scary, "but we handled it," although "they tried to kill us."
The robbery came less than a fortnight after an armed robbery at Kaikohe McDonald's, where three men armed with an axe and a shotgun smashed their way through the front door and ordered staff to hand over money. They have not yet been caught.