Math is Hard Sometimes

I bought a coffee at Quickie today for 99 cents. With tax, it came to $1.04. I gave the clerk 3 quarters, 2 dimes, and 2 nickels. He counted my change, looked up at me and said “This isn’t enough.”
I asked to see the change, figuring I’d forgotten a quarter or something. But there was enough there.
“See,” I said, pointing to his right hand, where he held my three quarters. “That’s 75.” Then I pointed at each coin in his left hand as I went: first dime “85″, second dime “95″, first nickel “a dollar”, second nickel “a dollar-five.”
“No,” he said, and pointed to the two nickels. “This is 10 cents. That’s not enough.”
“Yeah, it’s 10 cents,” I said, and proceeded to repeat myself: ” So, 75, 85, 95, a dollar, a dollar-five.”
“No, these are 10 cents,” he said, pointing AGAIN to my two nickels.
“OK, yeah,” I said. “That makes it 75, 85, 95, a dollar, a dollar-five.”
“No,” he repeated. Pointing to the dimes and the nickels in his hand, he said, “This is thirty cents!”
“Yes,” I agreed. “It is. So 75, 85, 95, a dollar, a dollar-five.” (in hindsight, it was pretty clear that this strategy wasn’t working, and I should probably have tried to math some other way.)
“No, it’s not enough,” he insisted. Thankfully, at that moment, his manager came over and said, “how much?” and then counted the change. “She’s right,” he said.
I thanked them and got the heck out of there, thankful that there was a manager around to confirm my math! Seriously though, this is the guy they have handling their money??