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	$148.61	8.730%	$161.5837	$161.58	$161.60	$161.60
Purchase #2	$40.27	10.208%	$44.3808	$44.38	$44.40	$44.40
Purchase #3	$43.96	12.276%	$49.3565	$49.36	$49.35	$49.40
Purchase #4	$216.42	4.325%	$225.7802	$225.78	$225.80	$225.80
Purchase #5	$127.83	13.762%	$145.422	$145.42	$145.40	$145.40
Purchase #6	$56.35	6.188%	$59.8369	$59.84	$59.85	$59.80
Purchase #7	$172.88	4.455%	$180.5818	$180.58	$180.60	$180.60
7 purchase totals =	$806.32		$866.9419	$866.94	$867.00	$867.00