chart x-axis numbering

I am using WinForms chart to visualize some data. I want x-axis gridlines at points specified by me. Please take a look at the following example.

public partial class Form1: Form
{
    public Form1()
    {
        InitializeComponent();            
        AddPoints();
    }

    public void AddPoints()
    {
        for (int i = 0; i <= 100; i++)
            chart1.Series[0].Points.AddXY(i, i);
    }
}

In the chart you can see the grid lines for X-Axis appears at 19,39,59,79 and 99. But I want it in 0,15,45,65,90,100. You can clearly see the interval is not the same. So setting the interval is of no use. Is it possible to have grid lines in my own specified point?