Hi and welcome to Just Answer!
Because you keep merchandise in California - your business has a nexus in that state and is responsible for taxes
First of all - before transacting intrastate business in California the business must first qualify/register with the California Secretary of State. (California Corporations Code section 2105, 15909.02, 16959 or 17451.) California Corporations Code sections 191, 15901.02(ai) and 17001(ap) define "transacting intrastate business" as entering into repeated and successive transactions
of its business in this state, other than interstate or foreign commerce.
For a Limited Liability Company - file an Application to Register (Form LLC-5) and attach to the completed form a valid certificate of good standing by an authorized public official of the foreign jurisdiction under which the foreign limited liability company is organized.www.sos.ca.gov/business/llc/forms/llc-5.pdf
Then - as a foreign LLC - your will be subject of franchise taxes
- regardless of your income - and might be required to collect sales taxes
from selling to California customers.
In additional - you need apportion your business income - and will be subject of income taxes
on the part of income attributable to California.
Let me know if you need any help.
Be sure to ask for clarification if needed.