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	$94.78	12.119%	$106.2664	$106.27	$106.25	$106.30
Purchase #2	$42.47	5.416%	$44.7702	$44.77	$44.75	$44.80
Purchase #3	$44.28	11.211%	$49.2442	$49.24	$49.25	$49.20
Purchase #4	$38.40	3.354%	$39.6879	$39.69	$39.70	$39.70
Purchase #5	$64.46	12.511%	$72.5246	$72.52	$72.50	$72.50
Purchase #6	$97.33	7.239%	$104.3757	$104.38	$104.40	$104.40
Purchase #7	$146.55	3.389%	$151.5166	$151.52	$151.50	$151.50
7 purchase totals =	$528.27		$568.3856	$568.39	$568.35	$568.40