Here is how I do it. It am starting from the assumption that anyone who sets there own watch will easily be a few seconds off, so I figure being accurate with the starting time within one minute is okay as long as I know the elapsed time is accurate.
As I am getting close to the location, I will start my lap timer at the 10 minute interval just before it just to make my math easier. I then use lap timing for the different parts. If I enter the location and my time throught the door is 7:34, time getting to the line is 7:42, time to order is 9:56, and time getting my food is 14:21, I can just adjust based on my start time. If I started my watch at 5:40, the times to enter are now 5:47:34, 5:47:42, 5:49:56, and 5:54:21.
I would not use the receipt times, because it is well documented here how often they are incorrect.