If we're talking "collector" pennies, then I assume the value should/would be similar to fiat prices. If it's the discontinued Canadian penny, I doubt they'll rise in value any time soon. Unless there's a place in the world where the exchange would make them valuable.
EDIT: And then I saw this:
https://bitcointalk.org/index.php?topic=269145.0;topicseenNow don't I feel stupid.