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	$183.83	3.134%	$189.5912	$189.59	$189.60	$189.60
Purchase #2	$53.36	11.505%	$59.4991	$59.50	$59.50	$59.50
Purchase #3	$149.85	4.364%	$156.3895	$156.39	$156.40	$156.40
Purchase #4	$116.49	4.303%	$121.5026	$121.50	$121.50	$121.50
Purchase #5	$209.74	8.643%	$227.8678	$227.87	$227.85	$227.90
Purchase #6	$203.71	9.201%	$222.4534	$222.45	$222.45	$222.50
Purchase #7	$165.64	4.749%	$173.5062	$173.51	$173.50	$173.50
7 purchase totals =	$1,082.62		$1,150.8098	$1,150.81	$1,150.80	$1,150.90