How much do you tip a wine tour driver/guide?

If you have a driver wine tour guide, tips are appreciated. This is especially the case if your guide goes above and beyond to enhance your experience like provide snacks, takes photos, is personable and makes you feel safe and does not rush. Amount-wise $5-$20 per couple is a nice range. Positive reviews on social media, especially TripAdvisor and Google mean a lot to the company and to the drivers. Be sure to mention them by name.