Pagination with my_query–>have_posts

How would I make pagination work with the following $my_query->have_posts coding? I’m well aware that the query method causes WP to ignore certain calls, but I understand there are work-arounds? I’ve tried implementing hacks from various websites, but none seem to work.

This is being used for a blog archive page, which shows the latest five posts. I’m just looking to add a “Older Posts | Newer Posts” navigation (pagination).

<?php
// page id 21 will get category ID 12 posts, page 16 will get category 32 posts, page 28 will get category 17 posts
if (is_page('5') ) {
$cat = array(3);
} elseif ( is_page('') ) {
$cat = array();
} elseif ( is_page('') ) {
$cat = array();
} else {
$cat = '';
}

$showposts = 5; // -1 shows all posts
$do_not_show_stickies = 1; // 0 to show stickies
$args=array(
   'category__in' => $cat,
   'showposts' => $showposts,
   'caller_get_posts' => $do_not_show_stickies
   );
$my_query = new WP_Query($args); 

?>

	<?php if( $my_query->have_posts() ) : ?>

		<?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
			<?php
			//necessary to show the tags
			global $wp_query;
			$wp_query->in_the_loop = true;
			?>