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	$104.56	11.491%	$116.575	$116.58	$116.60	$116.60
Purchase #2	$131.52	3.497%	$136.1193	$136.12	$136.10	$136.10
Purchase #3	$190.49	7.800%	$205.3482	$205.35	$205.35	$205.30
Purchase #4	$197.47	3.372%	$204.1287	$204.13	$204.15	$204.10
Purchase #5	$153.79	10.497%	$169.9333	$169.93	$169.95	$169.90
Purchase #6	$42.61	6.253%	$45.2744	$45.27	$45.25	$45.30
Purchase #7	$53.76	4.385%	$56.1174	$56.12	$56.10	$56.10
7 purchase totals =	$874.20		$933.4963	$933.50	$933.50	$933.40