She jailed Moataane for three years and four months for the aggravated robbery and to concurrent sentences of nine months and four months for the assaults.
Moataane's background involved "the all-too familiar litany of a violent upbringing and ... decline into violence, drugs and crime", defence counsel Cam Robertson told the court.
Counsel Amanda Bryant appeared for the Crown.
A Crown summary of facts said that Moataane, a patched member of the Mongrel Mob Rogue chapter, robbed the Puketapu Store about 5.15pm on July 24 last year.
The summary said he held the 14cm knife to the assistant's chest so that it was sticking up close to her face and neck.
She passed him a basket, which he began filling with cigarette packets, but told him her boss was coming when he yelled at her for cash.
Moataane grabbed the cigarettes and ran out of the shop to a vehicle with false plates and a getaway driver parked across the road.
The car was spotted by police a short time later in Flaxmere and Moataane was caught with several packets of cigarettes in his trousers.
Judge Mackintosh said Moataane was in an exercise yard at Manawatu Prison on November 28, when he threw a rugby ball and then "a number of punches" at another inmate.
On January 5, he punched a prison officer in the face, causing bruising and concussion. The officer was on ACC for a while on a reduced income.
Judge Mackintosh said Moataane, from Tonga, came to New Zealand as a child, struggled with language at school and became "somewhat marginalised", not thriving in his education and leaving without qualifications.
He got into trouble from the age of 17, became dependent on methamphetamine and cannabis, and spent time in and out of prison in between orchard jobs.
Moataane became affiliated to the Mongrel Mob, "somewhat disconnected" from his family and had perhaps relied upon the gang environment to fill the family role.
"That choice hasn't done you any good in the long term," Judge Mackintosh said.
A staff member at the store on Monday said that the victim in the robbery no longer worked there.