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	$140.51	3.805%	$145.8564	$145.86	$145.85	$145.90
Purchase #2	$136.51	9.155%	$149.0075	$149.01	$149.00	$149.00
Purchase #3	$155.42	11.365%	$173.0835	$173.08	$173.10	$173.10
Purchase #4	$93.39	13.190%	$105.7081	$105.71	$105.70	$105.70
Purchase #5	$177.89	6.507%	$189.4653	$189.47	$189.45	$189.50
Purchase #6	$206.73	10.874%	$229.2098	$229.21	$229.20	$229.20
Purchase #7	$108.70	13.717%	$123.6104	$123.61	$123.60	$123.60
7 purchase totals =	$1,019.15		$1,115.9410	$1,115.95	$1,115.90	$1,116.00