How can I calculate dynamic NYC limo fare estimates using a distance matrix API?

I'm working on a transportation booking system for New York and I'm trying to build a dynamic fare estimator for different pickup and drop-off locations.

The application needs to calculate the driving distance and estimated travel time between two addresses using a distance matrix or routing API. Based on the returned distance, I then want to apply different pricing rules for a private car or limo service.

For example, the pricing logic could include:

A minimum/base fare A per-mile or per-kilometer rate Different rates for longer trips Optional airport or toll fees Additional charges based on vehicle type Rounding the final estimated fare to two decimal places

I'm considering using a distance matrix API to retrieve the actual driving distance rather than calculating the fare from straight-line distance.

A simplified calculation would be something like:

distance = API driving distance

if distance <= minimum_distance: fare = base_fare else: fare = base_fare + (distance - minimum_distance) * rate

What would be the recommended way to structure this calculation so that the distance returned by the API can be reliably converted into a dynamic fare?

I'm particularly interested in best practices for handling API responses, units (miles vs. kilometers), rounding, and separating the API distance calculation from the fare-pricing logic.

The application is related to bespoke transportation new York, but the technical problem is specifically about implementing the distance-based pricing logic.

I'm affiliated with the transportation business mentioned above, so I'm disclosing that relationship here.