It's an English poshgirl way of abbreviating the word "totally".
I watched all of Switch (English Charmed. AWFUL!) recently which is painful and the villainesses were inbred poncy privileged trust-fund meangirl bitches who thought that they had to say "totes" at the end of every sentence to emphasize how serious they were about any given subject.
I do hope you totes understand that I was totes saying totes ironically, totes.
(Seriously, at the end of every sentence.)