I have been asked to be the power of attorney for an aunt. This would include paying all her bills, taking care of her checking account,talking to her financial advisors and making decisions about her accounts,. is there any guidelines on ?what is a resonable fee for doing this.

When you were asked, was a fee mentioned? Do you have an estimate of how much time you will need to spend on these tasks?

I would estimate anywhere from $25-$100/hour as reasonable. A lot depends on the amount of wealth the aunt has.

If you have to take off work to do things for her, your salary or hourly rate could be a guide. Can you ask her what she thinks is reasonable or is that not possible?
I have been researching POA laws in the state of PA for my own purposes to update our own POA's. They recommend a fee be "reasonable" (same as your words)and PA requires the Agent to sign a statement when he/she becomes an agent acknowledging:
I shall exercise the powers for the benefit of the principal.
I shall keep the assets of the principal separate from my assets.
I shall exercise reasonable caution and prudence.
I shall keep a full and accurate record of all actions, receipts and disbursements on behalf of the principal.

I would want my Agent to be rewarded and not financially burdened themselves but we seldom know for how long we will have to subsist- tough call. An Office on Aging dept. or similar in your area might have some thoughts on the subject. In some cases, government employees act on behalf of seniors who have no one to act on their behalf. An employee who does that might make $ 50K per year (?) and that hourly rate could be a guide. I think that comes to about $ 25 per hour as scott suggested as a starting point. Travel expenses would be in addition to that.
Bear in mind that the records you are probably required to maintain might be reviewed by Medicaid if your aunt gets involved with nursing home Medicaid support.