the nickle and penny are losing value due to inflation, and the price of manufacturing them is exceeding the value.
It would seem that an efficient way to lower the national dept would be to eliminate unnecessary expenses, and I believe that getting rid of the penny and nickle would do that.
some other countries have already rid themselves of the penny and had little to no negative drawbacks because of it.
for more information see the following videos: http://www.youtube.com/watch?v=y5UT04p5f7U
http://www.youtube.com/watch?v=77C47XYm_3c