CarouselView.DroidRenderer.cs

void SnapScroll ()
{
    var roughIndex = (float)_scrollView.ScrollX / _scrollView.Width;

    var targetIndex = 
        _deltaX < 0 ? Math.Floor (roughIndex)
        : _deltaX > 0 ? Math.Ceil (roughIndex)
        : Math.Round (roughIndex);

    ScrollToIndex ((int)targetIndex);
}

void ScrollToIndex (int targetIndex)
{
    var targetX = targetIndex * _scrollView.Width;
    _scrollView.Post (new Runnable (() => {
        _scrollView.SmoothScrollTo(targetX, 0);
    }));
}