interviewing

Now interviewing engineers for a job in our team (612643 available at intel.com web site). There are few candidates but so far no real 100% match... Soon there may be one more opening in Israel, related to Android development.

The question is, if there is a candidate that I can see is "no hire" in first 5 minutes of interview, would it be polite to tell sorry and stop the interview or I have to continue for another 25-55 minutes? I do the later but feel stupid meanwhile.