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	$224.52	9.679%	$246.2513	$246.25	$246.25	$246.30
Purchase #2	$123.65	3.195%	$127.6006	$127.60	$127.60	$127.60
Purchase #3	$191.34	9.545%	$209.6034	$209.60	$209.60	$209.60
Purchase #4	$126.52	4.406%	$132.0945	$132.09	$132.10	$132.10
Purchase #5	$77.88	6.747%	$83.1346	$83.13	$83.15	$83.10
Purchase #6	$81.86	4.687%	$85.6968	$85.70	$85.70	$85.70
Purchase #7	$92.36	9.103%	$100.7675	$100.77	$100.75	$100.80
7 purchase totals =	$918.13		$985.1487	$985.14	$985.15	$985.20