Question: Is there a way where we can edit the final selling price for Job/Estimate ?
Answer: When you create an estimate or create a job the pricing engine generates the price basis. The pre-tax price is made up of the price basis + markup/down + shipping charges. The tax is then applied to the pre-tax price to arrive at the sales price.
If you want to adjust the sales price you can manipulate the Pre-tax price field, so yes you can have final control over the sales price.