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	$189.64	5.362%	$199.8085	$199.81	$199.80	$199.80
Purchase #2	$127.86	5.217%	$134.5305	$134.53	$134.55	$134.50
Purchase #3	$70.25	3.768%	$72.897	$72.90	$72.90	$72.90
Purchase #4	$178.85	12.152%	$200.5839	$200.58	$200.60	$200.60
Purchase #5	$219.62	3.537%	$227.388	$227.39	$227.40	$227.40
Purchase #6	$47.42	12.361%	$53.2816	$53.28	$53.30	$53.30
Purchase #7	$47.57	10.378%	$52.5068	$52.51	$52.50	$52.50
7 purchase totals =	$881.21		$940.9963	$941.00	$941.05	$941.00