Rather have my actions support the employees.
I would even feel guilty to make them work when they aren't actually needed. Indeed, in the current system if they don't work they don't get money, but to me it's a wealth distribution problem. I'd rather have them get the same money and do whatever they like. It would be a net gain for society and a loss for nobody.
I bet many would rather do a useless job than staying at home getting Hartz IV.
I bet many would rather do hiking, writing or going to the cinema if they were paid the same. And since their job is useless already, it wouldn't change much. It wouldn't actually be a loss for anyone compared to the situation now (modulo the price of the machines and their maintenance, which is much less than a cashier's salary). However, replacing them with machines and giving them less money is a win for the shareholders, and that's what counts most in our system.
I've seen whole development teams that were more useless then that.
Furthermore, if there is less work to be done in supermarkets, then people can spend more time doing more interesting/productive work or simply enjoying their leisure. The issue is not that this (or any) automation is destroying people's livelihoods, but that the value added is being predominately captured by the already wealthy.
Portugal does suffer from an excess of 'work is for the workers' mindset, which is part of the reason it is so poor (compared to other Western European countries).