Another offender, Kaipara Anderson, 19, who was armed with a screwdriver and a pair of scissors during the hold-up was sentenced in January to five years and 10 months.
Five staff were threatened and bound before the shift manager was made to open the safe on the night of May 28, last year.
At yesterday's sentencing, Crown prosecutor Jarred Scott submitted Nathan's role should not be treated any different to other offenders and the fact he wasn't aware of the firearm did not diminish his culpability.
But defence lawyer Sumudu Thode said Nathan's culpability was vastly different to that of Cameron who had planned the robbery much earlier.
She said Nathan offered to help police locate the firearm used in the robbery and that the offer still stood.
Nathan was arrested after police located 30 gold and silver rings at his house in Dargaville.
Justice Matthew Palmer said Nathan offended while he was at a low point and saw his life
disintegrating before his eyes.
He agreed to be the getaway driver while struggling financially but admitted it was the "worst mistake" he'd made in his life.
The judge accepted Nathan was genuinely remorseful as he'd offered to help locate the firearm, agreed to participate in a restorative justice conference, and to pay reparation.
"I urge you to hold true to your intentions and set your life back on track," Justice Palmer said.
He said it was important Nathan stayed away from further offending otherwise he'd have to serve any future sentences in full given his second strike warning.
Fines of more than $6000 was remitted.
