Answer:
He should pay $ 20.97 for the bottle of cologne.
Explanation:
Given,
The cost of the bottle of cologne = $ 19.98,
Also, the amount of sales tax = $ 0.99,
Hence, the total amount paid by a customer for the bottle of cologne = cost of the bottle of cologne + sales tax
= $ 19.98 + $ 0.99
= $ 20.97