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	$21.58	4.635%	$22.5802	$22.58	$22.60	$22.60
Purchase #2	$95.78	4.817%	$100.3937	$100.39	$100.40	$100.40
Purchase #3	$173.34	10.177%	$190.9808	$190.98	$191.00	$191.00
Purchase #4	$49.60	3.530%	$51.3509	$51.35	$51.35	$51.40
Purchase #5	$58.91	5.851%	$62.3568	$62.36	$62.35	$62.40
Purchase #6	$5.62	8.301%	$6.0865	$6.09	$6.10	$6.10
Purchase #7	$103.78	7.119%	$111.1681	$111.17	$111.15	$111.20
7 purchase totals =	$508.61		$544.9170	$544.92	$544.95	$545.10