I am executor of my dads estate and was his power of attorney can I claim a fee for expenses in this case to cover my time and costs

I would keep track of hours and out of pocket expenses. Maybe $20/hr, including driving places, phone calls, everything. If you work and your time is worth more, charge what you make.
Some don't charge anything, depending on how much work it is; others charge a flat round amount.
I want my executor to ship several items to people, so will include a large flat rate for several hours of extra time, plus postage. Also dealing with any pets I might have left behind.

Nothing to 5% is common. Depends on the relationship with other parties. I was my mothers and did 1% with my sister.

A % seems so meaningless to me. My mom left 3 of us 70K. My dad left a little money, but a million dollar piece of land with a ratty old house on it. The neighbors wanted to buy the property instantly. Not much work for even 1% of a million.

Most (maybe all) states have mandated maximum rates that professionals such as estate attorneys may charge for executor services, and they are outlandishly high (perhaps because it's lawyers who write the laws). These fees are typically determined by the value of the estate, not its complexity or the number of hours it takes to perform all the tasks involved. However, as a family member, and a non-professional, I would advise that you only be reimbursed for your expenses, not for your time. Being an executor for your father's estate is a duty that you are being asked to perform for the good of the family. However, as suggested by joypulv you should not be stuck with expenses that you incur, such as travel expenses. You should keep good records of these expenses - you have a fiduciary responsibility to the estate that says it should pay only legitimate expenses.

As Ebaines suggests, OP shouldn't charge anything unless it is specifically approved by the court and, in such case a rate will probably be set by statute or rule. The will or other document appointing OP should also authorize fees, and hopefully the rate.