Tipping has been a part of every culture even here in Cryptocurrency we practice tipping, we humans are generous its inherent to us to give a guy something for a service he renders to us, it's like saying thank you for going the extra mile to a guy so I don't see anything wrong if you give a tip especially after you won a big amount, and the tip depends on your generosity, there is no minimum or maximum to a generous guy, but you will not be tag a good person for giving tip or bad for not giving one.
So I'll definitely give a tip whenever I win and more when the guy gives me good service with a smile.