I have been stacking pre 82 pennies for years, that is the way to go in my opinion.
Currently:
pre 82 pennies have a metal value of =$0.0238623
nickels have a metal value of = $0.0517926
http://www.coinflation.com/So you more than double your investment with the penny, not so much with the nickel.
The downside is that you have to sort the pennies. A lot of people hand sort, but if you want to get serious about sorting you can grab one of these:
http://www.pennysorter.com/I usually go to the bank and grab $100 worth of pennies at a time, sort them, and return the 83 and older pennies into the change machine at the bank, with a zero processing fee. I love my bank! 1 out of every 4 or so boxes I find an Indian head penny, and a few handful of Wheaties too, and I can sell those on ebay for added profit.
Ill also do this with dime and quarter boxes treasure hunting silver. I usually find 1 silver coin per box in the dimes and quarters. You have to hand sort those though, but it is fast work, looking at the edges of the coins for lines.