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	$85.47	11.370%	$95.1879	$95.19	$95.20	$95.20
Purchase #2	$67.90	4.763%	$71.1341	$71.13	$71.15	$71.10
Purchase #3	$224.66	12.685%	$253.1581	$253.16	$253.15	$253.20
Purchase #4	$148.51	5.387%	$156.5102	$156.51	$156.50	$156.50
Purchase #5	$158.88	6.549%	$169.2851	$169.29	$169.30	$169.30
Purchase #6	$13.82	6.823%	$14.7629	$14.76	$14.75	$14.80
Purchase #7	$104.61	6.232%	$111.1293	$111.13	$111.15	$111.10
7 purchase totals =	$803.85		$871.1676	$871.17	$871.20	$871.20