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	$92.87	10.534%	$102.6529	$102.65	$102.65	$102.70
Purchase #2	$226.64	3.323%	$234.1712	$234.17	$234.15	$234.20
Purchase #3	$72.83	7.537%	$78.3192	$78.32	$78.30	$78.30
Purchase #4	$216.39	5.749%	$228.8303	$228.83	$228.85	$228.80
Purchase #5	$124.29	7.667%	$133.8193	$133.82	$133.80	$133.80
Purchase #6	$154.70	11.627%	$172.687	$172.69	$172.70	$172.70
Purchase #7	$53.80	5.312%	$56.6579	$56.66	$56.65	$56.70
7 purchase totals =	$941.52		$1,007.1378	$1,007.14	$1,007.10	$1,007.20