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	$158.45	9.249%	$173.105	$173.11	$173.10	$173.10
Purchase #2	$29.27	11.281%	$32.5719	$32.57	$32.55	$32.60
Purchase #3	$228.40	7.183%	$244.806	$244.81	$244.80	$244.80
Purchase #4	$240.53	13.160%	$272.1837	$272.18	$272.20	$272.20
Purchase #5	$103.57	7.461%	$111.2974	$111.30	$111.30	$111.30
Purchase #6	$92.34	10.352%	$101.899	$101.90	$101.90	$101.90
Purchase #7	$138.28	11.245%	$153.8296	$153.83	$153.85	$153.80
7 purchase totals =	$990.84		$1,089.6926	$1,089.70	$1,089.70	$1,089.70