The issue with mandatory taxation is that the powerful in society will always corrupt the system somehow to pay what they are happy to pay (paying taxes or doing charity can be good investments reputation-wise) while everyone else will have to pay "their fair share".

As soon as everyone start using loopholes they will simply lobby to make it harder, to keep the powerful safe and everyone else paying. From anecdotal evidence, I'm pretty sure the religious route you recommend won't work.

The only way to make things fair in terms of taxes would be to have zero mandatory taxes. With zero taxes there is no-one benefitting from corrupting politicians. Career politicians would not exist anymore because there would be no more money in it.

Without taxes you're left with the problem of organising society without a central entity, eg. by having private police and protection, private healthcare, private education, private roads and by supporting those without means through voluntary charities instead of mandatory taxes.