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	$159.48	8.434%	$172.9305	$172.93	$172.95	$172.90
Purchase #2	$103.36	5.231%	$108.7668	$108.77	$108.75	$108.80
Purchase #3	$42.25	4.814%	$44.2839	$44.28	$44.30	$44.30
Purchase #4	$97.94	13.576%	$111.2363	$111.24	$111.25	$111.20
Purchase #5	$96.29	13.141%	$108.9435	$108.94	$108.95	$108.90
Purchase #6	$215.87	3.832%	$224.1421	$224.14	$224.15	$224.10
Purchase #7	$247.77	11.232%	$275.5995	$275.60	$275.60	$275.60
7 purchase totals =	$962.96		$1,045.9026	$1,045.90	$1,045.95	$1,045.80