Database Design for Multi site POS system

Question

I am trying to develope POS application which have three Point :-

1. POS Application Terminal (in the same store, Multiple)- for sell the goods (Mutiple terminal in same shop) Each terminal should have a local database for it's own inventory list and invoice. (Local database to avoid internet failure).

2. Backoffice (in the same store, single, Local Database)- Act as a parent for all the POS Application Terminal to get report and update the price to all the POS Application Terminal. All the POS Application Terminal (in single site) will send data to this database to generate the report like total goods sold.

3. Headoffice (Remote database- will get data from all the backoffice database)- This database will get data from all the backoffice from all the sites from different location. can send a price update to all the backoffice system and all the POS Application Terminal.

Can someone please provide me suggestion what kind of desing i should use or any database replication tool can help me in this condition.

Currently my application is fully ready and working with single local database, if i need to change the database design or anything to make it applicable as i mention above i am ready for any major change.

I am using Hibernate as ORM and MYSQL as a database.

Thanks