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	$162.84	7.560%	$175.1507	$175.15	$175.15	$175.20
Purchase #2	$111.71	7.188%	$119.7397	$119.74	$119.75	$119.70
Purchase #3	$140.28	8.189%	$151.7675	$151.77	$151.75	$151.80
Purchase #4	$60.58	9.657%	$66.4302	$66.43	$66.45	$66.40
Purchase #5	$126.89	7.849%	$136.8496	$136.85	$136.85	$136.80
Purchase #6	$122.46	5.386%	$129.0557	$129.06	$129.05	$129.10
Purchase #7	$217.97	10.345%	$240.519	$240.52	$240.50	$240.50
7 purchase totals =	$942.73		$1,019.5124	$1,019.52	$1,019.50	$1,019.50