Why do angry people buy chocolate?

So it's been bugging me now since Saturday so I'll just blog about it and then forget it... deal?
So I was closing Saturday night with my friend Mindy and around 7 this man and his son came in. There was only one other couple in store so it was pretty slow. I stood up and asked the Man how his night was going. He ignored me. No big people barely ever hear me anyway. So then he picked his candy. 3 two dollar bags. Who knew those bags were on a 3 for 5 deal... yeah not me. That must have happened over the past three days that I didn't work. So the total came to 6.41 and I told him. He said "how much is the tax rate?" I said "I don't know what the tax rate it was but it .41 cents." He said "aren't those three for five?" I looked for the sign and said "oh they are I didn't know that" So I re rang them up and took the dollar off making them five dollars plus tax made them 5.41. I was extremely confused because that is the same amount of tax it was for the six dollar total. So he then started to get angry and asked me what the tax rate was...again. I didn't know still because it'd been TWO MINUTES. So he said "Erase that transaction and make it a five dollar transaction" Which is was before the subtotal but whatever. I just took it all off AGAIN and press five dollars "bulk candy" one of the buttons so the subtotal was 5 dollars and then I pushed tax and it was like .36 cents. Soooo confusing. But he was like "is there a manager here" I said "no she's only here in the mornings usually." He said "How can I get a hold of her" (pretty dumb man) I said "you can come in or call" He said "well can I get that number" So Mindy who was sitting there the whole time saying nothing gets him a business card and he said "write your name on it too" So I wrote "adrienne" only it looks a little more like "adrimu" sometimes I write sloppy no big. So then he left and my night was horrible-r after that. AWESOME.