Adding extra charges

Hi, I am new here and a newbie with ERPNEXT. On my quotation, I have tax added which is ok. After the tax I want an additional registration fee to be added. Like registering a car an extra amount that is done after calculating the tax. How do I add that? I have checked quite a number of ways. it doesn’t seem to be working. I made a new item on sales taxes and charges temple thinking chargers will be an extra amount under the tax. There’s no option showing up to add a “registration fee” under the tax. How can I add this? Thank you.