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	$229.59	10.121%	$252.8268	$252.83	$252.85	$252.80
Purchase #2	$54.72	13.790%	$62.2659	$62.27	$62.25	$62.30
Purchase #3	$98.86	12.782%	$111.4963	$111.50	$111.50	$111.50
Purchase #4	$44.74	6.188%	$47.5085	$47.51	$47.50	$47.50
Purchase #5	$166.45	4.294%	$173.5974	$173.60	$173.60	$173.60
Purchase #6	$76.40	6.747%	$81.5547	$81.55	$81.55	$81.60
Purchase #7	$236.38	3.181%	$243.8992	$243.90	$243.90	$243.90
7 purchase totals =	$907.14		$973.1488	$973.16	$973.15	$973.20