If you're collecting tax, you have to mark it on any, statement, invoice or receipt.
As a rule, you'll be required to collect tax for purchases delivered to addresses within your home state, however out of state deliveries may or may not have the same requirements.
Do a Google search using the term "Amazon.com New York Taxes" to find out what can go wrong if you're not compliant with out-of-state tax laws.
Check with your competitors and run through a few test purchases to see what they're doing. Just keep changing the address without completing the checkout process.
Additionally, contact an Accountant or eCommerce expert in California. They'll have some helpful advice.
This might help:
Online Sales Taxes
Here's a great Article as well:
Sales Tax Collections for Online Sales
Good Luck