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