Found this on the web:

why do coins have reeded edges?

The question of the day at Ask Yahoo was Why do dimes and quarters have ridged edges while nickels and pennies have flat edges?

The short answer is two-fold. One, to keep people from shaving off the sides of the silver dimes and quarters (when they were made of silver) and two, because it helps visually impaired people distinguish the coins.
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Reader comments (Add your own)

That's interesting...I've never even thought about it before.

But there are no precious elements in these chips. So were they made for blind gamblers? I still like my easy-to-handle theory.

Robert