Quinten is right on this.
That is what the per diem is for, so you don't need to track receipts throughout the year.
Since we are under DOT regulations that is why we get the $59 per day unlike others who get per diem they have to get the per diem for each city they are in and the rates are all over the board.
Now if you go in to Canada then the per diem rate is $65 per day.
On profit gauges it asked you how many days you were out for each month. Just give that Number of days to your accountant at the end of the year.
Don't get it confused with the 80% though, some people will give their accountant the number with the 80% figured in and the he will take another 80% and mess it all up. Just give him the days you were out and make sure he knows the rate.
Right now it is $59 but keep an eye out because the IRS publishes it in October it could go up and then you will use the new rate for the last 2 months if it does.