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	$56.86	10.175%	$62.6455	$62.65	$62.65	$62.60
Purchase #2	$24.51	12.274%	$27.5184	$27.52	$27.50	$27.50
Purchase #3	$50.63	7.193%	$54.2718	$54.27	$54.25	$54.30
Purchase #4	$100.58	13.276%	$113.933	$113.93	$113.95	$113.90
Purchase #5	$65.36	8.769%	$71.0914	$71.09	$71.10	$71.10
Purchase #6	$155.70	13.461%	$176.6588	$176.66	$176.65	$176.70
Purchase #7	$52.83	5.603%	$55.7901	$55.79	$55.80	$55.80
7 purchase totals =	$506.47		$561.9090	$561.91	$561.90	$561.90