In reply to:

It's strange how we don't make the coin sizes in order of value.

Like almost everything else, things today are the way they are because they are unchanged from what suited before. Originally, the sizes of the coins approximated actual values. The penny, made of copper, contained about 1 cent of value. The nickel, made of nickel, contained about 5 cents worth of nickel. The dime, made of silver, contained about 1/10th of a dollar's worth of silver. Quarters and half-dollars were also silver, and are thus were progressively larger. I think dollar coins were initially gold, but changed to silver a long time ago. Although the metallic content of the coins has since changed, the sizes initially established have remained.