I wonder what it would look like if the stack was filled with one dollar bills rather than 100s. I'm sure the visualization would be quite mind boggling.
hah sorry had to.. but seriously would be crazy!
http://www.kokogiak.com/megapenny/sixteen.asp
And if that's not enough, one quadrillion pennies:
http://www.kokogiak.com/megapenny/seventeen.asp
and if that's still not enough, one quintillion pennies: