using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

          decimal val = 0.999999999632381M;

            var roundOffValue = 100000;

            var OriginalValue = Math.Round(val, 5);

            var OriginalValue_WithCustomLogic = Math.Round(Math.Floor(val * roundOffValue) / roundOffValue, 5);

        Console.WriteLine("OriginalValue: " + OriginalValue);

        Console.WriteLine("decimal.ToInt32(val * roundOffValue) "+decimal.ToInt32(val * roundOffValue));

        Console.WriteLine("Math.Floor(val * roundOffValue)" + Math.Floor(val * roundOffValue));

        Console.WriteLine("OriginalValue_WithCustomLogic: " + OriginalValue_WithCustomLogic);

​

    }

}