Hi, wonnderboy, and welcome aBoard.

"Penny" has been in Englsih usage as the basic coin for a very long time indeed - long before we started to colonise the New World. My guess is that the word came over with the colonists and became stuck in the language.
The other possibility is that it has evolved from the German "pfennig" (it has a common root with penny) but I think the first is the most likely