Well, that seems unlikely. 
I’m not clear what you are trying to accomplish.
I see the results I expect:
Dim neg As Double = -0.10
Dim floor As Double = Xojo.Math.Floor(neg) // -1.0
Dim ceil As Double = Xojo.Math.Ceil(neg) // 0.0
Dim round As Double = Xojo.Math.Round(neg) // 0.0