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	$98.60	12.616%	$111.0394	$111.04	$111.05	$111.00
Purchase #2	$223.62	13.108%	$252.9321	$252.93	$252.95	$252.90
Purchase #3	$98.87	8.501%	$107.2749	$107.27	$107.25	$107.30
Purchase #4	$230.52	10.850%	$255.5314	$255.53	$255.55	$255.50
Purchase #5	$156.69	8.142%	$169.4477	$169.45	$169.45	$169.40
Purchase #6	$100.63	13.490%	$114.205	$114.21	$114.20	$114.20
Purchase #7	$155.49	6.214%	$165.1521	$165.15	$165.15	$165.20
7 purchase totals =	$1,064.42		$1,175.5826	$1,175.58	$1,175.60	$1,175.50