SKULabs does not directly provide rates to your Ecommerce software, however most software today already supports calculated shipping rates during checkout.
With that said, the best answer is: you don't need to include calculated shipping rates at checkout. Allowing selection for specific carrier services or methods is simply not in a seller's best interest, especially when there are outages at UPS or FedEx.
Instead, we recommend only offering free, tiered, or flat-rate shipping at checkout. This makes fulfilling orders less rigid and increases sales by reducing the amount of indecision possible during checkout.