I bill by the hour, not the minute. If I work 10 mins on something and do nothing for the other 50, you are billed an hour. Frankly, this is how most clients have actually wanted it. They think in hours (or days) not some subdivision of them. And yes, thinking about work is the same as doing the work. It's all billable time. As far as your rate, I always bill as high as I can without pushback. Where is that level? Yo…
I deal with a lot of contractors. To be clear: If I asked for a single task that takes 5 minutes and they bill me an hour for it, that's 100% fine in my book. Context switching, recording, billing, etc. aren't free. The difference between a 60-minute bill and a 10-minute bill is nothing. Let's just keep it simple and bill an hour.
But this is only for individual tasks. If someone is working independently on a project with 10 minutes here, 15 minutes there, 5 minutes a few hours later and billing each as an hour, that's not okay.
Depending on the contractor, we don't really scrutinize line items all that closely. However, once you're dealing with multiple contractors and gathering experience about how long things generally take, you start to notice some contractors are outliers in how many "hours" they claim to get things done. In some cases, if their hourly rate is low enough we may not really care, but when someone hits the combo of billing a high hourly rate and also racking up a lot of hours for relatively simple things with no ability to explain why it took longer than everyone else, it's time to phase out that contractor.