As soon as we're talking about customers with accounts, we're no longer in the same ballpark as the original post. I don't have an account at every place I buy coffee. I shouldn't need to. I don't have an account at the three supermarkets I use
Whenever you don't pay with physical cash(paper money) you are paying with an account - either charging to a store account or a debit account or a credit card account.
The emergence of Cryptocurrencies on the scene will not change this. You will still be paying from an "account" - it will just be a cryptocurrency account.
We will not see blockchain transactions at the point of sale on any kind of scale (e.g. large stores and supermarkets) where there is a high turnover of sales.
you might not see "blockchain transactions" but you will see some indication that the transaction is "ok" ie: the red light turn green, or a final receipt, after the requisite number of confirmations is achieved.