The 1/8 dollar was a feature of the old Spanish dollar (hence the term "pieces of eight", the eight pieces being known as "bits" -- "two bits" is then a quarter), which is where the Americans got it in the first place. In fact, up to 2001 American stock exchanges expressed prices in 1/8 and 1/16 dollar increments (apparently 1/16 was only introduced at the NYSE in 1997).