Any way I can give a bonus to seller?
This is not available in Fiverr, only the Price of the GIG and if there was any Extras he added and you as a buyer selected them!
Gegeneo is “also correct” in that the only unit for a bonus is $5 units.
Madmoo has valiantly “fought”(?) to have a modified tip system added to fiverr. So far her brilliance hasn’t won the day or presents issues the principles are unwilling to state or resolve.