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	$154.82	11.324%	$172.3518	$172.35	$172.35	$172.40
Purchase #2	$222.32	7.363%	$238.6894	$238.69	$238.70	$238.70
Purchase #3	$113.41	4.704%	$118.7448	$118.74	$118.75	$118.70
Purchase #4	$111.72	5.493%	$117.8568	$117.86	$117.85	$117.90
Purchase #5	$178.88	11.570%	$199.5764	$199.58	$199.60	$199.60
Purchase #6	$125.89	10.445%	$139.0392	$139.04	$139.05	$139.00
Purchase #7	$89.81	10.395%	$99.1457	$99.15	$99.15	$99.10
7 purchase totals =	$996.85		$1,085.4041	$1,085.41	$1,085.45	$1,085.40