He opened the till and started to hand the money over when the robber moved behind the counter next to him. That's when he thrust the weapon into Mr Meghwal's stomach.
"His face was covered with some sort of cloth but really all I could look at was the barrel of that gun pushing into my stomach."
"I started to take money out of the till but then he just grabbed what he could himself and took off."
Apart from the three customers, Mr Meghwal and another staff member were the only others in the store.
He said the three women just dropped to the ground and lay on the floor when the robber burst in.
"I rang 111 as soon as the man left and the police were here before I'd finished the call."
He was thankful no one was hurt and said the three women were shaken but otherwise fine. Mr Meghwal would not say how much the robber had made off with but said it was a "significant amount".
"He took our takings for the entire day and we'd been very busy yesterday," he said.
Whanganui Police said the offender was a male about 1.73m (5ft 7in) to 1.76m (5ft 8in) tall of medium build. He was wearing dark clothing and his face was covered.
After fleeing the shop he got into a small white hatchback, similar to a Mazda Familia or Toyota Corolla, that was parked in St Leonard St near the store.
The store's owner, Bhim Chouhan, is currently overseas, but Mr Meghwal rang him and told him of the robbery.
Mr Chouhan has owned the store for nine years and this is the sixth time it has been targeted. The previous five burglaries had all been at night.
Cigarettes had always been taken in earlier break-ins and in March 2010 - the last time the store was burgled - thieves made off with about $10,000 worth of cigarettes.
In February this year the store reopened after a major rebuild, changing from the St John Foodmarket to St John Four Square Supermarket.
Whanganui police say they would like to hear from anyone who may have information on the robbery, the small white hatchback vehicle, or who may have seen anything suspicious in the area at the time of the robbery.
Anyone with information can call Constable Paul Heathcote at the police station on 349 0618. All information will be treated confidentially.