Offline Database for Web Application

I want to build a web application that can run offline on desktop, and to achieve that I'm using Electron and io.js

The application will basically consist in a data management system for a grocery store, where the user will insert/get data refering to the sales, expenses, stock, etc...

At this moment i'm struggling to choose which database suits me better. So far I've looked into a few solutions like: MongoDB, CouchDb and IndexedDB.

I was hoping that someone could shed me some light on this matter. Thanks.