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	$146.58	6.234%	$155.7178	$155.72	$155.70	$155.70
Purchase #2	$53.53	12.553%	$60.2496	$60.25	$60.25	$60.20
Purchase #3	$106.59	5.120%	$112.0474	$112.05	$112.05	$112.00
Purchase #4	$156.61	11.208%	$174.1628	$174.16	$174.15	$174.20
Purchase #5	$66.93	8.802%	$72.8212	$72.82	$72.80	$72.80
Purchase #6	$220.55	6.858%	$235.6753	$235.68	$235.70	$235.70
Purchase #7	$150.67	5.436%	$158.8604	$158.86	$158.85	$158.90
7 purchase totals =	$901.46		$969.5345	$969.54	$969.50	$969.50