You really need a good cheap mileage tracking app if you deduct business miles. I have tried Mile IQ and Triplog for Android and I like them both.
Mile IQ does fully automatic drive detection. After you've been out driving, swipe the drives right for business and left for personal. It's really easy, and it's free for the first 40 drives a month ($5.99/month for more). You will have to go in and name your destinations, but it learns. E-mail yourself the report at the end of the year. You do have to leave the app turned on. There's no way to manually enter a drive after the fact.
Triplog allows you to manually enter drives. I've been using this for a while because I don't drive enough to want to leave an app running all the time. There is a start/stop button for GPS tracking. The free version allows you to e-mail yourself monthly report. The paid version ($1.50/month + several more levels) allows you to get one report for the whole year.
Triplog also has a paid (really inexpensive) browser version that offers fleet management with GPS map tracking and graphic reports!
QuickBooks Online doesn't have a mileage tracking feature at all. I miss that from the desktop version. But since mileage is a tax deduction and not a cash transaction, it doesn't really belong there. Just give your mileage reports to your CPA.
I send all my clients who track mileage a reminder on New Years to write down their odometer reading. The IRS wants to know the beginning and ending readings for the year.