Tennessee Code Title 56. Insurance § 56-7-3202

(a) When a patient's out-of-pocket cost for a prescription or covered service is percentage-based, the covered entity or pharmacy benefits manager shall calculate the out-of-pocket cost such that when the out-of-pocket cost is added to the amount that the covered entity or pharmacy benefits manager will directly pay to the pharmacy or other dispenser the sum will equal the actual reimbursement.

(b) The requirements of subsection (a) shall not apply when patient out-of-pocket cost for a prescription or covered service is percentage-based for only a specified portion or predefined subset of drug tiers or specialty drug categories and the remainder of the covered drug prescriptions or services available to the patient are associated with predefined and specific out-of-pocket costs.