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	$65.83	4.231%	$68.6153	$68.62	$68.60	$68.60
Purchase #2	$177.28	4.300%	$184.903	$184.90	$184.90	$184.90
Purchase #3	$230.85	3.704%	$239.4007	$239.40	$239.40	$239.40
Purchase #4	$159.67	8.705%	$173.5693	$173.57	$173.55	$173.60
Purchase #5	$104.88	13.670%	$119.2171	$119.22	$119.20	$119.20
Purchase #6	$144.48	5.605%	$152.5781	$152.58	$152.60	$152.60
Purchase #7	$129.37	10.711%	$143.2268	$143.23	$143.25	$143.20
7 purchase totals =	$1,012.36		$1,081.5103	$1,081.52	$1,081.50	$1,081.50