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	$66.88	8.599%	$72.631	$72.63	$72.65	$72.60
Purchase #2	$127.34	5.363%	$134.1692	$134.17	$134.15	$134.20
Purchase #3	$29.82	4.313%	$31.1061	$31.11	$31.10	$31.10
Purchase #4	$50.54	7.203%	$54.1804	$54.18	$54.20	$54.20
Purchase #5	$57.68	7.748%	$62.149	$62.15	$62.15	$62.10
Purchase #6	$198.27	4.127%	$206.4526	$206.45	$206.45	$206.50
Purchase #7	$30.70	3.840%	$31.8789	$31.88	$31.90	$31.90
7 purchase totals =	$561.23		$592.5672	$592.57	$592.60	$592.60