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	$162.48	6.395%	$172.8706	$172.87	$172.85	$172.90
Purchase #2	$40.40	9.485%	$44.2319	$44.23	$44.25	$44.20
Purchase #3	$71.70	11.766%	$80.1362	$80.14	$80.15	$80.10
Purchase #4	$43.55	7.726%	$46.9147	$46.91	$46.90	$46.90
Purchase #5	$14.25	4.663%	$14.9145	$14.91	$14.90	$14.90
Purchase #6	$27.99	5.485%	$29.5253	$29.53	$29.55	$29.50
Purchase #7	$95.88	13.117%	$108.4566	$108.46	$108.45	$108.50
7 purchase totals =	$456.25		$497.0498	$497.05	$497.05	$497.00