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	$116.65	9.583%	$127.8286	$127.83	$127.85	$127.80
Purchase #2	$150.39	10.821%	$166.6637	$166.66	$166.65	$166.70
Purchase #3	$34.84	6.823%	$37.2171	$37.22	$37.20	$37.20
Purchase #4	$105.74	12.509%	$118.967	$118.97	$118.95	$119.00
Purchase #5	$140.47	10.443%	$155.1393	$155.14	$155.15	$155.10
Purchase #6	$145.71	3.832%	$151.2936	$151.29	$151.30	$151.30
Purchase #7	$37.39	10.704%	$41.3922	$41.39	$41.40	$41.40
7 purchase totals =	$731.19		$798.5015	$798.50	$798.50	$798.50