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	$217.82	9.399%	$238.2929	$238.29	$238.30	$238.30
Purchase #2	$130.50	3.315%	$134.8261	$134.83	$134.85	$134.80
Purchase #3	$203.88	5.318%	$214.7223	$214.72	$214.70	$214.70
Purchase #4	$34.59	10.694%	$38.2891	$38.29	$38.30	$38.30
Purchase #5	$191.78	12.350%	$215.4648	$215.46	$215.45	$215.50
Purchase #6	$158.55	4.796%	$166.1541	$166.15	$166.15	$166.20
Purchase #7	$232.50	6.620%	$247.8915	$247.89	$247.90	$247.90
7 purchase totals =	$1,169.62		$1,255.6408	$1,255.63	$1,255.65	$1,255.70