The coins were variously made of aluminum, plastic, or even cardboard. The purpose was to "save" the customer from being overcharged when he paid the sales tax on small purchases, say a dime on which the tax at 2% would be two mills and paying a penny would lose the customer 4/5th cent. Not paying at all would cost the state 2/5th cent, hence the creation of the tax token. Different states issued different denominations, 1,2, and 5 mill values.
The use of these tokens prevailed throughout the thirties and into the forties. Eventually someone figured out that the whole thing was too cumbersome, yet the government could not afford to simply eliminate the sales tax, so the bracketed tax was devised. Say at 2% the table would indicate a tax on purchases of one to twenty-four cents would be zero; from twenty=five to seventy-four cents, one cent tax; seventy-five to $1.24, two cents, and so on. This required the publication of sales tax tables for the merchant and the general public. Which of course was not cumbersome.. Or perhaps it was, who knows? This method is still being used in some states, Except of course a two-percent tax is a long-dead dream. Also some municipalities have jumped on the bandwagon and imposed their own sales taxes in addition to the statewide taxes. In some states these now total as much as 9.45%. Ours is seven percent except in certain cities where it is more, at least on some items.
And. Some states have a tiered system in which the tax rates vary for different items purchased.
The mind of man is infinitely convoluted and forever seeking more ways to complicate our lives.
Image:By $1LENCE D00600D at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=32892050