Denying the state revenue keeps its evil deeds in check. "Meter feeding" is "illegal" (in some areas), but not for any objective or rational reason. Keep people from getting parking tickets, and the local tyrants have less funds to misuse. The silver coins idea is pretty neat, too. I carry around a 1964 silver quarter in my wallet. I like to take it out every now and then and show it to people to demonstrate what's been done to our money. I compare it with the fake quarters they have in their pockets. All I really have to do is drop my real coin on a table top and compare the sound it makes with their phony coin's pathetic clank.
My silver quarter is worth almost $5.00 based on its melt value (the value of the metals, 90% silver, 10% copper, that it contains). This is why real money retains its buying power, while the funny money forced on us by the state has had its value stolen from us by inflation.
So, I go to a seller who will allow me to buy, say, $4.00 worth of goods for my silver 25 cents. Since the quarter is still valid United States currency, the sales tax on the transaction is on 25 cents, not 4 dollars! More loss of revenue for our evil overlords! Oh yeah!
U.S. Silver Coin Melt Value Calculator