I think it depends on where you are. I asked at Chase a couple of years ago and was told that the computer won't let them order halves. The head teller said that she tried to order some for someone else and when she processed the order, the number changed to 0 for halves. A few months later, she told me that they received a memo stating that "half dollars and large dollar coins are no longer considered circulating currency and cannot be ordered". I made them my dump bank until my car loan was paid off (yes, I paid my car loan in halves).
Scott