I make my logbook match what I do as closely as possible. There are always places where you have a choice to make about which 15 minute block is the most correct, and there are times that applying the laws and company policy will put you in technical violation.
Like at my company we are required to include the entire 15 minute block when we hang up the fuel pump as on duty. So lets say that I start out from home at 8am and it is 51 miles to my fuel stop. I can make that trip in 51 minutes and fuel within 6 minutes. So I can stop the fuel pump at 8:58 and log the 51 miles of driving in 45 minutes followed by 15 minutes to fuel. The only problem is that this exceeds the companies speed limit policy coming in at 68 miles per hour. Oops dang I just made an illegal log entry. Did I log it as I did it? Yes. Was it completely legal and within company policy? No. So my personal rule is to have it match within 15 minutes of actual events.
In another case we are required to log 30 minutes for any DOT roadside inspection that includes the times listed on the report. Last month I had an inspection that only took ten minutes from 9:20 to 9:30 and I was on a tight schedule so I couldn't hang around for and extra fifteen minutes at the end, so I logged the 30 minutes from 9:00 to 9:30. I left the weight station at 9:31 with a legal looking log, but I was actually driving for 15 minutes between 9:00 and 9:15 that showed on my log as on duty at the weigh station.
What! I am puzzled by them telling you 30 minutes automatically. DOT even tells you to log the amount of time I had you stopped. The time start and finish is on that inspection. If you was stopped for 15 minutes or less then you should only have to log 15 minutes. Now if you was put out of service you BETTER make sure you stay for the amount of time written on that inspection. But that's just crazy

to make you log 30 every time (like it happens allot). That's telling you to falsify your log actually. They are telling you the amount of time to log when they have proof you was only there for 15 minutes. You would be driving the other 15 minutes (more than likely, right).
I always tell drivers log how long it took you (most things are going to take a MINIMUM of 15 minutes) to deal with it. If I tell you to log 15 minutes for fueling and it took you 30 minutes and you log 30. I told you to falsify your log sheet. Now it's plan common sense fuel, loading, scaling etc is going to take @ least that 15 minutes!
This amounts to required falsification of logbooks by the very rules that we are supposed to follow. With such restrictive laws it is impossible to follow them completely. Follow the spirit of the law and you will be fine. Stay within your 14 and take a full 10 hour break. If you think about it there is no reason to exceed your 14 if you are going to take a break anyway because no matter when you take your break during your trip you will arrive at the same time in theory.