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	$94.51	10.158%	$104.1103	$104.11	$104.10	$104.10
Purchase #2	$176.77	11.431%	$196.9766	$196.98	$197.00	$197.00
Purchase #3	$141.70	11.540%	$158.0522	$158.05	$158.05	$158.10
Purchase #4	$156.39	10.413%	$172.6749	$172.67	$172.65	$172.70
Purchase #5	$111.27	6.852%	$118.8942	$118.89	$118.90	$118.90
Purchase #6	$220.37	8.657%	$239.4474	$239.45	$239.45	$239.40
Purchase #7	$118.96	7.797%	$128.2353	$128.24	$128.25	$128.20
7 purchase totals =	$1,019.97		$1,118.3909	$1,118.39	$1,118.40	$1,118.40