Yes, going forward, it will simplify your record-keeping to always separate business and personal purchases.
If you want to deduct the sales tax, then yes, you will need to compute that as well. You aren't required to do this, it would only benefit you by increasing the cost of your baking supplies. Depending on the state you live in, it might not be material to you if groceries aren't taxed.
Here is an article you may find helpful: Reporting Self-Employment Business Income and Deductions
