Moving models on a grid not centered?

Hello. I'm working on a model moving and placing function for a tycoon. However, when I go to place a model, the model is not centered and this causes the player to be able to place his model off the grid a little bit. I'm not sure what the problem is buts frustrating me and is a decent sized chunk of code. If someone wouldn't taking a look and seeing what the problem is it would be much appreciated.

If you need to see the problem go to my place and experiment with placing models from your inventory on to your baseplate on the edges https://www.roblox.com/games/1656142905/Rocky-Mountain-Mining-EARLY-ACCESS

while placing do
	if Mouse.Target then
		if Mouse.Target:IsDescendantOf(GetTycoon()) and Mouse.Target.Name == "BasePlate" then
			local TycoonBase = Mouse.Target
			local TycoonBaseSizeX, TycoonBaseSizeZ
			local HitboxSizeX, HitboxSizeZ 
			
			if Rotation % 180 == 0 then
				TycoonBaseSizeX, TycoonBaseSizeZ = TycoonBase.Size.x, TycoonBase.Size.z
				HitboxSizeX, HitboxSizeZ = Hitbox.Size.x, Hitbox.Size.z
			else
				TycoonBaseSizeX, TycoonBaseSizeZ = TycoonBase.Size.x, TycoonBase.Size.z
				HitboxSizeX, HitboxSizeZ = Hitbox.Size.z, Hitbox.Size.x
			end
			
			local TycoonTopLeft = TycoonBase.CFrame * CFrame.new(Vector3.new(TycoonBase.Size.x/2, 0, TycoonBase.Size.z/2))
			local BaseAngleX, BaseAngleY, BaseAngleZ = CFrame.new(TycoonBase.Position, (TycoonBase.CFrame*Vector3.new(1, 0, 0))):toEulerAnglesXYZ()
			local VectorRotation = CFrame.Angles(BaseAngleX, BaseAngleY, BaseAngleZ)
			
			local RoundByThreeX = RoundByThree(math.floor(Mouse.Hit.p.x - TycoonTopLeft.x))
			local RoundByThreeZ = RoundByThree(math.floor(Mouse.Hit.p.z - TycoonTopLeft.z))
			
			if RoundByThreeX < -TycoonBaseSizeX + HitboxSizeX then
				RoundByThreeX = RoundByThreeX + HitboxSizeX
			end
			
			if RoundByThreeZ < -TycoonBaseSizeZ + HitboxSizeZ then
				RoundByThreeZ = RoundByThreeZ + HitboxSizeZ
			end
			
			local VectorComponent1 = CFrame.new(Vector3.new(TycoonTopLeft.x, Mouse.Target.Position.y, TycoonTopLeft.z))
			local VectorComponent2 = CFrame.new(Vector3.new(RoundByThreeX, Mouse.Target.Size.y/2, RoundByThreeZ))*VectorRotation
			local VectorComponent3 = CFrame.new(Vector3.new(-HitboxSizeX/2, Hitbox.Size.y/2, -HitboxSizeZ/2))
			
			local NewVector = VectorComponent1*VectorComponent2*VectorComponent3
			
			
			local RegionVectorMin = NewVector * CFrame.new(Vector3.new(HitboxSizeX/2, -Hitbox.Size.y/2, HitboxSizeZ/2))
			local RegionVectorMax = NewVector * CFrame.new(-Vector3.new(HitboxSizeX/2, -Hitbox.Size.y/2, HitboxSizeZ/2))
			
			local Hitboxes = game.Workspace:FindPartsInRegion3(
				Region3.new(
					Vector3.new(
						math.min(RegionVectorMin.x, RegionVectorMax.x),
						math.min(RegionVectorMin.y, RegionVectorMax.y),
						math.min(RegionVectorMin.z, RegionVectorMax.z)
					) + Vector3.new(0.1, 0, 0.1),
					Vector3.new(
						math.max(RegionVectorMin.x, RegionVectorMax.x),
						math.max(RegionVectorMin.y, RegionVectorMax.y),
						math.max(RegionVectorMin.z, RegionVectorMax.z)
					) - Vector3.new(0.1, 0, 0.1)
				), nil, 100
			)
			
			local ModelColliding = false
			for i, Hitbox in pairs(Hitboxes) do
				if Hitbox.Name == "Hitbox" and not Hitbox:IsDescendantOf(Visual) then
					ModelColliding = true
				end
			end
			
			if not ModelColliding then
				LastPosition = NewVector * CFrame.Angles(0, math.rad(Rotation), 0)
			end
			Visual:SetPrimaryPartCFrame(LastPosition)
		end
	end
	wait()
end
--end of placing