To set Sales Tax to be charged for your state only:
Go to admin and on the left click on Location/Taxes
Then click on Tax Zones
Then click on the Yellow Folder (it should of been set up with your state, if not see how to set that below) so your yellow folder should say your state.
Then click on edit
Then put in your country and put in your state
then click update
If you did not set up your state and zone this is what you do:
go to Location/Taxes
then taxes zones
Then click on insert
In the zone name put in your state and in the description put in your state