Why do some coins have grooves on the edges? And why are they there?
The dollar, half-dollar, quarter, and ten-cent coin denominations were originally produced from precious metals (gold and silver). Reeded edges were eventually incorporated into the design of these denominations to deter counterfeiting and the fraudulent use of the coins, such as filing down the edges in an attempt to recover the precious metals.
The one-cent and five-cent pieces are considered "minor" coins of the United States and with the exception of the wartime nickel, produced from 1942–1945, other minor coins never contained precious metals.
Currently, none of the coins produced for circulation contain precious metals. However, the continued use of reeded edges on current circulating coinage of larger denominations is useful to the visually impaired. For example, the ten-cent and one-cent coins are similar in size; the reeding of the ten-cent coin makes it easily identifiable by touch.