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	$66.25	10.485%	$73.1963	$73.20	$73.20	$73.20
Purchase #2	$99.95	11.547%	$111.4912	$111.49	$111.50	$111.50
Purchase #3	$99.88	12.200%	$112.0654	$112.07	$112.05	$112.10
Purchase #4	$247.90	5.256%	$260.9296	$260.93	$260.95	$260.90
Purchase #5	$89.91	10.472%	$99.3254	$99.33	$99.35	$99.30
Purchase #6	$140.25	9.327%	$153.3311	$153.33	$153.35	$153.30
Purchase #7	$232.88	8.735%	$253.2221	$253.22	$253.20	$253.20
7 purchase totals =	$977.02		$1,063.5611	$1,063.57	$1,063.60	$1,063.50