Think about it this way. A nickel's melt value is a little over .04. So that 80% or so of it's face value. Pre 82 pennies melt value is over .02, which is more than 200% of its face value. So with 5 pennies, you have .10 of melt value whereas the nickel is .04.
I also keep pre 82 pennies, hoping once they remove/replace it in circulation they will be able to be melted. People on ebay buy them too so once I have enough , might just sell em.