If you are purchasing raw materials used in manufacturing, that means you are sales tax-exempt and should never pay sales tax on those ingredients. Sales tax is only paid once (by the end consumer). When purchasing sales tax-exempt raw materials, most states require that you submit a sales tax exemption certificate (aka reseller's permit) to every vendor; otherwise, you must pay sales tax. The state will seek both tax & penalties during an audit if you don't pay sales tax or haven't supplied the correct paperwork.
The Lupulin Exchange has dedicated a lot of resources toward creating a streamlined, frictionless experience for managing sales tax exemption certificates. To learn more about how it works and what you'll need, go here.
If you are purchasing hops for some other purpose (ie personal use) and don't intend to resell them or use them in manufacturing, then you are not exempt from sales tax and will need to make your purchase elsewhere.