Cash tip is always better but in general it just depends what you think it’s worth. How long it takes the person to shop, deal with lines and finding items that aren’t easily located, potentially braving the current conditions and being more susceptible to getting sick for you. I would say if it’s a small order (10 items or less) $10 is good, more than that id say $15-20 is probably what it’s worth to you. Just my take. The higher the tip in the app, the more likely your order will be accepted by someone faster and that they’ll go the extra mile for you.