Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$17.60	9.524%	$19.2762	$19.28	$19.30	$19.30
Purchase #2	$104.47	6.552%	$111.3149	$111.31	$111.30	$111.30
Purchase #3	$196.53	9.136%	$214.485	$214.49	$214.50	$214.50
Purchase #4	$79.43	13.409%	$90.0808	$90.08	$90.10	$90.10
Purchase #5	$166.55	4.293%	$173.7	$173.70	$173.70	$173.70
Purchase #6	$247.27	5.267%	$260.2937	$260.29	$260.30	$260.30
Purchase #7	$230.38	12.605%	$259.4194	$259.42	$259.40	$259.40
7 purchase totals =	$1,042.23		$1,128.5700	$1,128.57	$1,128.60	$1,128.60