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	$190.33	13.426%	$215.8837	$215.88	$215.90	$215.90
Purchase #2	$197.50	12.649%	$222.4818	$222.48	$222.50	$222.50
Purchase #3	$193.39	6.310%	$205.5929	$205.59	$205.60	$205.60
Purchase #4	$166.52	13.261%	$188.6022	$188.60	$188.60	$188.60
Purchase #5	$157.45	6.453%	$167.6102	$167.61	$167.60	$167.60
Purchase #6	$217.31	4.714%	$227.554	$227.55	$227.55	$227.60
Purchase #7	$37.64	3.790%	$39.0666	$39.07	$39.05	$39.10
7 purchase totals =	$1,160.14		$1,266.7914	$1,266.78	$1,266.80	$1,266.90