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	$204.38	4.507%	$213.5914	$213.59	$213.60	$213.60
Purchase #2	$95.78	9.116%	$104.5113	$104.51	$104.50	$104.50
Purchase #3	$51.71	8.748%	$56.2336	$56.23	$56.25	$56.20
Purchase #4	$86.75	3.786%	$90.0344	$90.03	$90.05	$90.00
Purchase #5	$184.45	12.703%	$207.8807	$207.88	$207.90	$207.90
Purchase #6	$122.39	6.532%	$130.3845	$130.38	$130.40	$130.40
Purchase #7	$117.72	8.653%	$127.9063	$127.91	$127.90	$127.90
7 purchase totals =	$863.18		$930.5422	$930.53	$930.60	$930.50