You don't absolutely need to keep it separated but be sure to save the amount for payment either quarterly or monthly depending on how often the dept. Of revenue requires you to file. You may be able to simply call a number, add a bank acct, enter the numbers, and pay the bill.
Doing this stuff really isn't that complicated. But like everything else in business and life, there's steps that need to be taken in order to proceed properly.
Good luck with your new venture. I hope it treats you well.