The price of a 6.5 oz Coke was fixed at about 5 cents from 1886 to 1959. This was due to many reasons, including competition, vending machines, etc. In 1953 Coke unsuccessfully tried to get the government to mint a 7.5 cent coin that could be used in vending machines that could not make change. They did not want to increase the price to 10 cents or force people to use pennies. From around 1950 to 1959 the price of a 6.5 ounce Coke started to vary around the USA. In 1951 Coke stopped advertising the 5 cent price and by 1959 the last of the 5 cent Cokes had been sold.
Source, Wikipedia