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	$103.76	4.324%	$108.2466	$108.25	$108.25	$108.20
Purchase #2	$110.65	5.189%	$116.3916	$116.39	$116.40	$116.40
Purchase #3	$77.59	11.217%	$86.2933	$86.29	$86.30	$86.30
Purchase #4	$182.90	8.748%	$198.9001	$198.90	$198.90	$198.90
Purchase #5	$154.31	4.509%	$161.2678	$161.27	$161.25	$161.30
Purchase #6	$53.50	3.525%	$55.3859	$55.39	$55.40	$55.40
Purchase #7	$126.30	10.504%	$139.5666	$139.57	$139.55	$139.60
7 purchase totals =	$809.01		$866.0519	$866.06	$866.05	$866.10