pos/pos_barcode_tare/pos_barcode_tare.xml

<odoo>
    <template id="assets_backend" name="pos_barcode_tare" inherit_id="point_of_sale.assets">
            <xpath expr="." position="inside">
                 <link rel="stylesheet" href="/pos_barcode_tare/static/src/css/pos_barcode_tare.css"/>
                <script type="text/javascript" src="/pos_barcode_tare/static/src/js/pos_barcode_tare.js"></script>
            </xpath>
    </template>
</odoo>