Mirror databases

I have a collection of databases that are meant to be equal in an array
of PCs. Specifically, it is about POS stations: each POS has exactly the
same tables of articles, cashiers, etc. They are meant to work in a
standalone fashion, so I can't afford the idea of all clients and one
server, and each one has to be client and server at the same time. If
the network has problems, the whole supermarket must operate in spite of
that.
So, if I have one PC that I will call "master", is there any native
mechanism in Postgre to duplicate automagically those tables to the rest
of the "slaves"? If I need to update them all, it would be enough to
update this master and tell the rest to "copy" the database from that
one. I wouldn't need to worry about the state of each box, and assume
that Postgre does it all for me, knowing what it needs to update in each
case.
Excuse me if my language is novice, but I am not very learnt in this
field.
Thank you in advance,

Leandro Fanzone.