He went full-time when he graduated from high school in 1939 and, with time out to serve in the military during World War II, stayed with the business until he retired in 2000.
Over the years, the business changed drastically.
"The biggest change is the variety and the number of items we've added. It's out of this world," he said. "Back then, we had two kinds of cereal - corn flakes and oatmeal. Now the assortment is fantastic and everything comes in umpteen sizes."
"We would write down what they wanted and then the list went to the office," he said.
"They would come in with a basket and take their shopping home in that," Hassler said.
The store maintained accounts for most of their customers, adding the prices of items purchased and deducting the cost of produce and other items people sold to the store.
The Hasslers have kept those old ledger books. One, begun in early 1926, shows that Uriah Fasnacht bought flour and other staples and, every week or so, sold 24 dozen eggs to the store.
The accounts were settled in April, with the customers either paying what they owed or, if the store bought more than it sold, getting cash payments.
The store was open late on Fridays and Saturdays, and opened at 5 weekday mornings so people who brought milk to the creameries could shop early.