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	$228.87	11.730%	$255.7165	$255.72	$255.70	$255.70
Purchase #2	$53.28	11.445%	$59.3779	$59.38	$59.40	$59.40
Purchase #3	$14.27	8.605%	$15.4979	$15.50	$15.50	$15.50
Purchase #4	$78.54	3.660%	$81.4146	$81.41	$81.40	$81.40
Purchase #5	$68.39	3.128%	$70.5292	$70.53	$70.55	$70.50
Purchase #6	$208.72	5.433%	$220.0598	$220.06	$220.05	$220.10
Purchase #7	$211.53	9.435%	$231.4879	$231.49	$231.50	$231.50
7 purchase totals =	$863.60		$934.0838	$934.09	$934.10	$934.10