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	$54.25	9.862%	$59.6001	$59.60	$59.60	$59.60
Purchase #2	$222.84	5.242%	$234.5213	$234.52	$234.50	$234.50
Purchase #3	$62.99	8.873%	$68.5791	$68.58	$68.60	$68.60
Purchase #4	$138.87	3.389%	$143.5763	$143.58	$143.60	$143.60
Purchase #5	$229.89	9.695%	$252.1778	$252.18	$252.20	$252.20
Purchase #6	$136.77	6.710%	$145.9473	$145.95	$145.95	$145.90
Purchase #7	$148.26	5.801%	$156.8606	$156.86	$156.85	$156.90
7 purchase totals =	$993.87		$1,061.2625	$1,061.27	$1,061.30	$1,061.30