Not true at all. The concept of "siesta" exists, but nobody does it at work. It's mostly something for retired people with a lot of free time and not much to do.
Only small shops do this, and it's more of a 1-to-4 thing. I guess they could... I don't know, have lunch, spend time with their family, do some chores?
Besides, you can't expect a small store with one or two employees (e.g. a bookshop) to be open from 9 AM to 8 PM without any breaks in between.