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	$118.79	6.563%	$126.5862	$126.59	$126.60	$126.60
Purchase #2	$136.53	5.164%	$143.5804	$143.58	$143.60	$143.60
Purchase #3	$81.71	5.222%	$85.9769	$85.98	$86.00	$86.00
Purchase #4	$13.75	9.320%	$15.0315	$15.03	$15.05	$15.00
Purchase #5	$158.34	4.374%	$165.2658	$165.27	$165.25	$165.30
Purchase #6	$56.62	8.637%	$61.5103	$61.51	$61.50	$61.50
Purchase #7	$102.28	10.332%	$112.8476	$112.85	$112.85	$112.80
7 purchase totals =	$668.02		$710.7987	$710.81	$710.85	$710.80