C#-Code

using System;
using System.Collections.Generic;

namespace Split5
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> numbers = new List<int> { 15, 1, 5, 88, -14, 7, -21, 42, 29, 36, 74 };

            foreach (int number in numbers)
            {
                double erg;
                double m = number % 5;
                if (m < 2.5)
                    erg = number - m;
                else
                    erg = number + (5 - m);
                Console.WriteLine(number + " => " + erg);
            }
            Console.Read();
        }
    }
}