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	$200.50	4.173%	$208.8669	$208.87	$208.85	$208.90
Purchase #2	$72.81	3.630%	$75.453	$75.45	$75.45	$75.50
Purchase #3	$76.32	4.679%	$79.891	$79.89	$79.90	$79.90
Purchase #4	$134.80	12.385%	$151.495	$151.50	$151.50	$151.50
Purchase #5	$59.88	11.552%	$66.7973	$66.80	$66.80	$66.80
Purchase #6	$106.49	11.359%	$118.5862	$118.59	$118.60	$118.60
Purchase #7	$233.67	10.603%	$258.446	$258.45	$258.45	$258.40
7 purchase totals =	$884.47		$959.5354	$959.55	$959.55	$959.60