Final answer:
The Store Manager's approval is needed for the guest to claim the Lowest Price Guarantee.
Step-by-step explanation:
When the guest presents the documentation for a "Lowest Price Guarantee" at the register, the approval of the Store Manager is needed. The Store Manager is responsible for making decisions and handling matters related to store policies and procedures, including price guarantees. They have the authority to approve or deny the guest's claim under the lowest price guarantee.