During my time as a Mason (I left for much the same reason as jayofdoom), we followed the same procedure when voting for new members. The couple of times there was a non-unanimous vote, the Master called for another vote, in case anyone made a mistake or wanted to reconsider. In none of the cases did anyone make a show of not voting or showing their votes, though. I think it only happened twice in the 12 or so years I was there. I have no idea why someone rejected one of the candidates; and in the other, I suspect some of our members thought the candidate wanted to join because he thought it would help him with a political career (this is purely speculation; we didn't discuss this at all).