using System;

using System.Collections.Generic;

using System.Globalization;

using System.Linq;

public class Program

{

    public static void Main()

    {

        // Should not be necessary outside of this fiddle

        CultureInfo usCulture = new CultureInfo("en-US");

        CultureInfo.CurrentCulture = usCulture;

        CultureInfo.CurrentUICulture = usCulture;

        // -fiddle

        var v = 999.9m;

        Console.WriteLine("Method X: " + Math.Round(v, 2));

        Console.WriteLine("Method A1: " + Math.Round(v, 2).ToString("C"));

        Console.WriteLine($"Method A2: {Math.Round(v, 2):C}"); 

        Console.WriteLine("Method B: $" + Convert.ToDecimal(v.ToString("F2")));

        Console.WriteLine(Math.Round(v, 2) == Convert.ToDecimal(v.ToString("F2")));

    }

}