Well... it's not really what you are eating, but the service you have received. When we go to our local Tapas bar, invariably we just have a bottle of cava or champers, and they always bring it to the table, and bring some nibbles. We always leave a tip.
I usually tip about 10%. Some people tip more, and some don't tip at all. The staff in bars in Ontario are on minimum wage, so they sort of depend upon tips to augment their income.
In a table service restaurant I tend to tip at about 10% on average but also take the view that a tip is a reward for good service. If I really feel I've been looked after I'll leave a bit more but occasionally when the service has been really bad I don't tip at all.