Any civil libertarian should rightly fear the imposition of a cashless society and what it represents to individual privacy.
Stores choosing to be cashless or not isn't an "imposition". The imposition is to ban cashless stores.
The dilemma is similar to how libertarians can cope with the rise of (ostensibly) private internet companies hoarding data. In theory, a libertarian will say that it's fine for private companies to hold this data and do whatever with it; in practice the fact that private companies and the government have a symbiotic relationship means that many libertarians (the ones I speak to, anyway) are just as sceptical of Google, Facebook et al as they are of the government. They - the government and big business alike - are imposing this cashless society upon us, and if you consider yourself libertarian or sceptical of government you are foolish to consider it some sort of benign change.
(Here crytocurrencies are largely a red herring. Society is not being ushered in that direction, it's being told to normalise a world where every single transaction, journey in public transit etc can both be monitored and mined for data)