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	$213.72	11.676%	$238.6739	$238.67	$238.65	$238.70
Purchase #2	$127.83	6.653%	$136.3345	$136.33	$136.35	$136.30
Purchase #3	$220.94	5.510%	$233.1138	$233.11	$233.10	$233.10
Purchase #4	$233.34	8.388%	$252.9126	$252.91	$252.90	$252.90
Purchase #5	$172.77	10.132%	$190.2751	$190.28	$190.30	$190.30
Purchase #6	$56.45	9.156%	$61.6186	$61.62	$61.60	$61.60
Purchase #7	$37.27	10.663%	$41.2441	$41.24	$41.25	$41.20
7 purchase totals =	$1,062.32		$1,154.1726	$1,154.16	$1,154.15	$1,154.10