If you have no other regular place of work the mileage deduction is door-to-door. You are working from home, though you may not actually be claiming a home office on your return. (Caution about claiming a home office as there are specific criteria it must meet, such as an exclusive use space. You can claim your equipment without claiming a home office on your return. If you own and claim a home office, you will be depreciating that portion of your home, which will lower your cost basis when you sell.)
Commuting mileage is not deductible if you have a normal place of business. So a salesman, for example, goes to his office to pick up his call sheet for the day. He returns to his office at the end of the day to turn in his paperwork. His mileage between his home and his office is not deductible because it is a commute. From the office he goes to visit clients A, B and C. The mileage from his office to the clients and back to his office is 'business mileage'.
A part timer works the mornings for company A and then goes to company B for the afternoon. Home to A is 'commute', A to B is 'business mileage' and then IRS gets vague whether the part timer needs to claim A to home as 'commute' or B to home as 'commute' if he/she does not return to A before going home.
The part timer situation above is where someone with a regular place of work who shops on the way to work, on lunch hour or on the way home gets touchy. A reasonableness approach I think is what is called for here in absence of specific example from IRS and unwillingness of IRS to give a specific answer (and believe me, I have tried). If it is 8.6 miles to work, you have 17.2 miles of 'commute' for a round trip. If from your driveway to work and then to shops and home has a total of 22.2 miles on your odometer, I would call 17.2 miles 'commute' and 5 miles deductible business miles.
I have never found anything in IRS statement or example that would contradict this approach and each year I read the guidelines to see if there have been any changes or clarifications.