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	$170.86	4.687%	$178.8682	$178.87	$178.85	$178.90
Purchase #2	$169.45	8.734%	$184.2498	$184.25	$184.25	$184.20
Purchase #3	$104.29	12.710%	$117.5453	$117.55	$117.55	$117.50
Purchase #4	$143.29	3.448%	$148.2306	$148.23	$148.25	$148.20
Purchase #5	$160.90	8.419%	$174.4462	$174.45	$174.45	$174.40
Purchase #6	$167.69	13.715%	$190.6887	$190.69	$190.70	$190.70
Purchase #7	$87.52	4.789%	$91.7113	$91.71	$91.70	$91.70
7 purchase totals =	$1,004.00		$1,085.7401	$1,085.75	$1,085.75	$1,085.60