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	$216.77	10.813%	$240.2093	$240.21	$240.20	$240.20
Purchase #2	$12.42	11.188%	$13.8095	$13.81	$13.80	$13.80
Purchase #3	$111.70	11.425%	$124.4617	$124.46	$124.45	$124.50
Purchase #4	$123.31	11.825%	$137.8914	$137.89	$137.90	$137.90
Purchase #5	$159.69	11.509%	$178.0687	$178.07	$178.05	$178.10
Purchase #6	$93.77	12.665%	$105.646	$105.65	$105.65	$105.60
Purchase #7	$70.98	9.578%	$77.7785	$77.78	$77.80	$77.80
7 purchase totals =	$788.64		$877.8651	$877.87	$877.85	$877.90