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	$165.91	4.532%	$173.429	$173.43	$173.45	$173.40
Purchase #2	$76.89	8.802%	$83.6579	$83.66	$83.65	$83.70
Purchase #3	$63.70	12.383%	$71.588	$71.59	$71.60	$71.60
Purchase #4	$23.65	6.571%	$25.204	$25.20	$25.20	$25.20
Purchase #5	$186.87	11.609%	$208.5637	$208.56	$208.55	$208.60
Purchase #6	$149.58	4.449%	$156.2348	$156.23	$156.25	$156.20
Purchase #7	$12.55	7.509%	$13.4924	$13.49	$13.50	$13.50
7 purchase totals =	$679.15		$732.1698	$732.16	$732.20	$732.20