Yes! For ShipStation accounts based in the US, Canada, Australia and New Zealand, the Rate Shopper feature allows you to create groups of services (called "Rate Shopper rules") you'd like ShipStation to compare. When you apply a Rate Shopper rule to a shipment (either manually or using an Automation Rule), ShipStation will compare the rates for all services in the strategy and automatically apply the lowest rate to the selected shipment(s).
Review the Rate Shopper: Automate Selecting the Lowest Rate help article for details on how to create and use Rate Shopper rules.