Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
Rest assured that the federal tax is collected by the federal government from the credit-card issuer in both cases. Amex chooses to offset that cost by charging a fee (equal to the tax) to the cardholder; Chase does not.