Hi,

You can use chrome.js to open it by using the openCashControl function.

Please try the following code

odoo.define('ModuleName.Chrome', function(require) {
    'use strict';
    const Chrome = require('point_of_sale.Chrome')

    const UpdatedChrome = Chrome =>
        class extends Chrome {
            openCashControl(){
                super.openCashControl();
                this.showPopup('YourPopup', {
                    // Args if any
                });
            }
        }

   Registries.Component.extend(Chrome, UpdatedChrome);
 
 });

Regards