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	$40.59	5.786%	$42.9385	$42.94	$42.95	$42.90
Purchase #2	$116.48	9.397%	$127.4256	$127.43	$127.45	$127.40
Purchase #3	$157.26	8.327%	$170.355	$170.36	$170.35	$170.40
Purchase #4	$247.91	3.188%	$255.8134	$255.81	$255.80	$255.80
Purchase #5	$128.67	4.593%	$134.5798	$134.58	$134.60	$134.60
Purchase #6	$200.41	12.412%	$225.2849	$225.28	$225.30	$225.30
Purchase #7	$67.62	11.459%	$75.3686	$75.37	$75.35	$75.40
7 purchase totals =	$958.94		$1,031.7658	$1,031.77	$1,031.80	$1,031.80