Check with the inspector and your local plumbing code. Usually 3" and under is 1/4" slope and above that is 1/8". Not enough slope and your solids will not move and too much slope will allow the fluid to pass by the solids so they don't move as well. Either way could end up with plugging and snaking down the road.
With a new house, you don't want to install it wrong and then have the inspector say to take it out and do it right.