You can't. In a cashless society, your purchases (and all the things one can infer from that: interests, location, day patterns) are surveilled 100% of the time.
"Cashless" is the elites and security apparatuses against the ability of the people to maintain their privacy and take away the last little vestiges of the disenfranchised to get by... it's a selfish, ignorant, utopian social experiment.