Sales tax refund-AMZ FBA

I own an LLC and have been filing sales tax on my own from the very beginning. Since AMZ collects and pays it, I file 0 as per the law. Now, the prob is that I do retail arbitrage and a lot of places refuse to acknowledge my sales and tax permit and charge me tax saying that they only exempt it for Non-profits, and they never reimburse it. So I end up paying the sales tax for most of my purchases. Since I file 0, and AMZ collects the sales tax on my behalf, I do not know how to file for a refund when I file the sales tax. Can someone please tell me how to get this refunded or deducted? I hope your answer does not involve dealing with Amazon seller- service because they are the worst people to deal with.