Yes!, we encourage tipping (or gratuities depending where you are from).
When you finish your ride, if you go back into the Shofer app you'll be asked to pay for your ride. Part of this process will present you a tip screen with a slide bar.
As you slide this bar along it will increase your ride value, this is then added to your ride cost as part of your trip.
Whilst we encourage you to tip, how much you tip is entirely up to you. It's also nice to let your driver know if you intend to tip them as you may make their day :).
Please see below a link to a video that provides an example of the tipping process