I would have to disagree with porcelain.dolly. Every class and audition experience I've had has taught me to sing something in the style of the show - whether it's from a musical or not. RENT was one of the first musicals of it's type - rock/pop opera - and that's exactly what the style is! Don't be afraid to sing a rock song, especially one from the mid 1980's - mid 1990's. Look at Pat Benatar or Heart or things like that.
If you want to sing something from a musical, look for something in the same style. I think something from "Hair" would be alright, also "The Who's Tommy", some of Stephen Schwartz's stuff (NOT WICKED), and also some of Elton John's musical work (I don't think "Strongest Suit" is a good audition song - there's too many parts to it. A cool idea would be to do a female version of "Fortune Favors the Brave" from Aida...you would definitely stand out!).
Hope this helps!!
BFA in Musical Theatre