Let me clarify, you don't have to send your official transcripts if you don't want to. If you did great and you think it will enhance your chances then send the offical one, but otherwise you could just fax the schools a copy of your grade report you get from your school.
When I applied when I was still in school, I faxed and email all my new grades to the schools where I had filled out secondaries. But I didn't pay to have any official transcripts sent.