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	$131.25	11.593%	$146.4658	$146.47	$146.45	$146.50
Purchase #2	$175.60	5.848%	$185.8691	$185.87	$185.85	$185.90
Purchase #3	$78.59	3.750%	$81.5371	$81.54	$81.55	$81.50
Purchase #4	$241.97	12.575%	$272.3977	$272.40	$272.40	$272.40
Purchase #5	$95.48	13.601%	$108.4662	$108.47	$108.45	$108.50
Purchase #6	$163.40	4.125%	$170.1403	$170.14	$170.15	$170.10
Purchase #7	$208.69	12.414%	$234.5968	$234.60	$234.60	$234.60
7 purchase totals =	$1,094.98		$1,199.4730	$1,199.49	$1,199.45	$1,199.50