Three men were jailed for a total of 19 years over the raid at Sunnyhill Stores, Wrenthorpe, Wakefield.
A judge commended the bravery of the shop assistant after the store was hit by an almost identical attack a year earlier.
Leeds Crown Court heard Wesley Harper, Michael Watson and Philip Littleford targeted the store on August 31 this year.
A customer had seen them behaving suspiciously outside the premises shortly before the robbery which took place at 6pm.
The customer went into the shop and warned the shop assistant to be careful.
She removed money from the till as a precaution moments before the men, wearing hoodies and with their faces covered, burst in holding a fake handgun and a knife.
Both weapons were pointed towards the woman and threats were made.
The assistant managed to back away from the men and press a panic button.
The robbers demanded to know were the rest of the cash was when they saw the till was almost empty.
They then left with a cancer charity box.
All three men, from the Lancashire area, were recognised from CCTV footage at another shop nearby as they had gone in without their disguises.
The car in which they were travelling also broke down on the M62 on the way home. They were caught on camera arranging for another car to pick them up.
They all three men pleaded guilty to robbery, possession of an imitation firearm and possession of a knife.
Watson, 33, of Raper Street, Oldham, and Harper 38, of Littlemoor Lane, Oldham, were both jailed for six years.
Philip Littleford, 36, of Vincent Avenue, Oldham, was the subject of a suspended prison sentence at the time of the raid. He was jailed for seven years.
Lawyers for the men said they had pleaded guilty to the offences at an early stage and were sorry for what they had done.
Jailing them, judge Neil Clark said: “You left (the victim) terrified. And what for? A very tiny amount of money which was there to help people with cancer.”
• Two men were jailed for a total of 24 years in May this year after they targeted Sunnyhill Stores during a 24-hour crime spree. One of the men was masked when he went into the store at 8.55pm on August 27 last year and pointed the weapon at the woman working behind the counter. She was ordered to hand over cash and cigarettes worth £400.