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	$208.28	11.337%	$231.8927	$231.89	$231.90	$231.90
Purchase #2	$71.45	6.504%	$76.0971	$76.10	$76.10	$76.10
Purchase #3	$133.40	13.296%	$151.1369	$151.14	$151.15	$151.10
Purchase #4	$17.87	5.334%	$18.8232	$18.82	$18.80	$18.80
Purchase #5	$103.25	3.311%	$106.6686	$106.67	$106.65	$106.70
Purchase #6	$127.83	9.482%	$139.9508	$139.95	$139.95	$140.00
Purchase #7	$118.31	10.439%	$130.6604	$130.66	$130.65	$130.70
7 purchase totals =	$780.39		$855.2297	$855.23	$855.20	$855.30