The Service Titan Equipment ID and the Service Titan Service ID are automatically marked as taxable in the Service Titan price book. Sales Builder Pro does this in case your company has tax set-up with the business unit associated with the job. If you do not want the Sales Builder Pro items to be taxable you have 2 options:
1) Search "sales builder pro" in the ST equipment price book and uncheck the taxable box, and repeat for the "sales builder pro" service item.
2) Remove tax from the business unit that you use for SBP jobs. If you use that business unit for other things besides SBP, that may not be the best way to go.