Yes, simply login to the web-based admin (/estore_admin), go to STORE SETUP > CHECKOUT SETUP > CHECKOUT URL, SSL SETTINGS & PAYMENT PROVIDER SELECTION and set the Checkout and/or SECURE URL to the shared SSL address for your account. The URL will vary but your ISP will provide you with the correct link (URL).

Usually the link will look something like: https://server001.myisp.com/mydomain