RoundingMode

 volume = Symbol.NormalizeVolumeInUnits(volume, RoundingMode.Down);

 using cAlgo.API;
 namespace cAlgo
 {
     // This sample shows how to normalize volume based on different rounding modes
     [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
     public class NormalizingVolumeSample : Indicator
     {
         [Parameter("Volume Unit", DefaultValue = VolumeUnit.Units)]
         public VolumeUnit VolumeUnit { get; set; }
         [Parameter("Volume Amount", DefaultValue = 0.01)]
         public double VolumeAmount { get; set; }
         [Parameter("Rounding Mode", DefaultValue = RoundingMode.ToNearest)]
         public RoundingMode RoundingMode { get; set; }
         protected override void Initialize()
         {
             double volumeInUnits = VolumeUnit == VolumeUnit.Units ? VolumeAmount : Symbol.QuantityToVolumeInUnits(VolumeAmount);
             double normalizedVolume = Symbol.NormalizeVolumeInUnits(volumeInUnits, RoundingMode);
             Print(normalizedVolume);
         }
         public override void Calculate(int index)
         {
         }
     }
     public enum VolumeUnit
     {
         Units,
         Lots
     }
 }