I think in the Netherlands the general rule is to tip up to 10% depending how good the service was, unless it was excellent and you go higher. When drinking a couple coffees in a restaurant it is okay to tip with a single Euro for good service, even if that doesn't amount to 10%.

This is despite the unfortunate and rude trend of payment devices now offering a big dickover screen filled with obscene tip suggestions first (25% in a fucking chain fastfood place?), because with the decline of cash the old way of rounding up the bill dies out too.