Coin Size- What's Up With That?

This one is for 26. She's a wonderful triceratops.

I've been thinking about something very strange. Dimes are smaller than a penny but they are worth ten cents and a penny is worth one cent. Why are dimes smaller than nickels and pennies? That's just bizarre. You know what else is crazy? A dollar is 100 cents but it's made out of paper and you can rip it right in half. But you can't rip a penny! What's up with that?