They shouldn't have been using the consumer version. I can sympathize, but that business both violated their license and ignored nine months of news and popups about the windows 10 update.
It seems we're talking about cash registers here. If their software happened to be running on Windows but the business bought them as self-contained devices, I'm not sure why the business staff would necessarily even have realised Windows was running on them, never mind been responsible for any software licence agreements or the like. The supplier of those cash registers might have made mistakes here, but the business staff are well justified in being upset at critical devices stopping working because of something like this.