The victim, who is a grandmother, was working behind the counter at the store North Moor Lane, Sunderland, when Conor Bates stormed in and demanded cash.
Newcastle Crown Court heard the till was opened and the 23-year-old raider left with the takings, leaving the terrified worker traumatised.
Newcastle Crown Court heard it was around 9.45pm on November 8, 2021, when Bates went into the shop, where there were other customers and ordered "open the till."
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Prosecutor Kevin Wardlaw said: "At first she thought he was playing a joke but then she realised he had a large knife with a 12 inch blade.
"He put the knife against her stomach and said again 'Open the till. I don't want to ******* hurt you'."
The victim, who had worked at the store for 16 years, opened the till and also pressed a panic button to alert her manager, who then got between the robber and her.
While taking £464, Bates said: "I'm sorry about this, I don't want to hurt anyone, I'm homeless".
In a victim impact statement, the shop worker said: "This has had a huge impact on my life in lots of ways.
"I've never been subjected to anything like this before. I've had threats before but I've not had someone pull a knife on me and it's caused so much distress and fear.
"I feel like my life has been put on hold."
She added that she was left "petrified" in case it happened again and feeling like a "prisoner in my own home".
She also said she had been unable to return to work and had not been able to go out to buy her children or grandchildren Christmas presents.
Bates, of no fixed address, who has 30 previous convictions, pleaded guilty to robbery and possessing an offensive weapon and was jailed for five years and four months with an extended licence period of a further two years.
Miss Recorder Davies said the extended sentence was for the "protection of the public" and told Bates: "The affect of your actions have been very significant indeed."
Jamie Adams, defending, said Bates left his family home at age 16 and is still very young and "immature".
Mr Adams said Bates had been trying to say "I'm not going to hurt you, just let me get the money" and did not use any actual violence.