all hard currency should be power of 2. see we would have a 2 cent penny, a four cent nickle and an 8 cent dime. the quarter would be 16 cents. there would be a rarely used 32 cent half dollar and a dollar would be 64 cents. bring back the $2 bill and make the $5 bill a $4 bill. your $10 would be replaces with an $8 and your $20 would be replaced with a $16 bill. you would then have a denomination for $32, $64, and $128. after that point its all snob notes (money that normal people never get to see), like the $256, $512, $1024, $2048, $4096 and so on. it would be a much better system than we have now. if you ever want to eliminate a denomination, say the 2 cent penny, then the next denomination is only twice as big. and so theres less of a rounding gap.
also no one pointed out that only about 3% of all money is actually in hard currency, and that will change as more people move to electronic transactions.