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	$69.27	5.261%	$72.9143	$72.91	$72.90	$72.90
Purchase #2	$231.26	13.560%	$262.6189	$262.62	$262.60	$262.60
Purchase #3	$138.71	11.492%	$154.6506	$154.65	$154.65	$154.70
Purchase #4	$190.25	10.164%	$209.587	$209.59	$209.60	$209.60
Purchase #5	$231.85	10.384%	$255.9253	$255.93	$255.95	$255.90
Purchase #6	$227.88	3.816%	$236.5759	$236.58	$236.60	$236.60
Purchase #7	$196.83	8.808%	$214.1668	$214.17	$214.15	$214.20
7 purchase totals =	$1,286.05		$1,406.4388	$1,406.45	$1,406.45	$1,406.50