Pennies, which are the smallest unit of american currency, are very expensive to make, costing around 2-3 cents. While this isn't a huge hole in the budget, only around 100 million dollars, it's still very obvious and seems like something that should be solved. For those who say this will cause higher prices and lower charitable donations, in New Zealand and Canada, where one cent currency has been eliminated, none of these things have occurred.
There are many videos about this, but one in particular is this one by CGPGrey: http://www.youtube.com/watch?v=y5UT04p5f7U.



