Please do not tip. We do not want to create a culture where this becomes part of the norm and thereby an expectation. To the best of my knowledge, hospitality staff are not taxed on presumptive tips and if such a culture is introduced this may well become the case and then those who are not being tipped are effectively being disadvantaged for the same work.
In Australia and New Zealand, laws ensure staff are paid a living wage and even the lowest paid workers are protected (theoretically) from exploitation by employers. The fiscal relationship exists between an employee and the employer, not the employer's customer. We don't want to give employers any justification for lowering wages or work standards. People have died to protect this right.
In my opinion, the only tip acceptable is to be kind to your mother and look both ways before you cross the road. Do not tip, please.