pos/pos_gift_ticket/views/pos_template.xml

<openerp>
    <data>

        <template id="pos_gift_ticket_assets_backend"
                  name="pos_gift_ticket_assets_backend"
                  inherit_id="point_of_sale.assets_backend">
            <xpath expr="." position="inside">
                <script src="/pos_gift_ticket/static/src/js/main.js"
                        type="text/javascript"></script>
            </xpath>
        </template>

    </data>
</openerp>