You can set the folders to 755 and the files to 644.
You need to leave the folder media with the permissions 777 as hikashop will have to write email and CSS modifications into it. If you use a version prior to 1.4.1, then, you should leave the front end folder (components/com_hikashop) to 777 until you upgrade.
In your case, since you had access rights issues, you will have to put them back to 777 when you update.