In countries where tipping is not compulsory (i.e. where serving the food is seen as an integrated and indispensable part of selling food to customers, and servers actually are paid the same way as other workers), rounding up to a logical round sum is both common and recommended.

If a server were to complain that a 19,72 % tip was rude, I would have rounded the tip down to a round and easily sharable $6.