Tax

I have an app and I wanted to know how would I make it so that when the user purchases something from the app it know the tax for each state and add it automatically for each state. Here is some of my code:

   if PKPaymentAuthorizationViewController.canMakePayments(usingNetworks: paymentNetworks) {
            let request = PKPaymentRequest()
            
            request.merchantIdentifier = "merchant.com.shiningdevelopers"
            request.countryCode = "CA"
            request.currencyCode = "CAD"
            request.supportedNetworks = paymentNetworks
            request.requiredShippingContactFields = [.name, .postalAddress]
            // This is based on using Stripe
            request.merchantCapabilities = .capability3DS
            
            let tshirt = PKPaymentSummaryItem(label: "T-shirt", amount: NSDecimalNumber(decimal:1.00), type: .final)
            let shipping = PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(decimal:1.00), type: .final)
            let tax = PKPaymentSummaryItem(label: "Tax", amount: NSDecimalNumber(decimal:1.00), type: .final)
            let total = PKPaymentSummaryItem(label: "Total", amount: NSDecimalNumber(decimal:3.00), type: .final)
            request.paymentSummaryItems = [tshirt, shipping, tax, total]
            
            delegate?.sendRequest(items: request.paymentSummaryItems)  
            
            let authorizationViewController = PKPaymentAuthorizationViewController(paymentRequest: request)
            
            if let viewController = authorizationViewController {
                viewController.delegate = self
                
                present(viewController, animated: true, completion: nil)
            }
        }
    }