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	$59.95	3.422%	$62.0015	$62.00	$62.00	$62.00
Purchase #2	$166.70	3.777%	$172.9963	$173.00	$173.00	$173.00
Purchase #3	$85.55	5.812%	$90.5222	$90.52	$90.50	$90.50
Purchase #4	$88.98	12.862%	$100.4246	$100.42	$100.40	$100.40
Purchase #5	$120.92	9.484%	$132.3881	$132.39	$132.40	$132.40
Purchase #6	$58.63	5.389%	$61.7896	$61.79	$61.80	$61.80
Purchase #7	$165.66	12.197%	$185.8656	$185.87	$185.85	$185.90
7 purchase totals =	$746.39		$805.9879	$805.99	$805.95	$806.00