Hi ethanjbeau302,
Since Bentley University's AVERAGE GMAT score is 580, your current score might be enough to get you in. I understand why you'd want to retest though (a higher score would make you a stronger applicant). With your current GMAT scores, you have an opportunity to pick up plenty of missing points in either the Quant or the Verbal sections.
To that end, I'm curious about how you've been studying and how you perform on Test Day:
1) How long have you been studying?
2) How long did you study before each of your Official GMATs?
3) What materials did you use during your studies?
4) Do you have a pacing problem in either the Quant or Verbal sections? Do you finish early? Do you have to rush at the end of the section just to finish (if so, then how many questions are you rushing through?)? Did you leave any questions unanswered?
GMAT assassins aren't born, they're made,
Rich