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	$128.25	6.112%	$136.0886	$136.09	$136.10	$136.10
Purchase #2	$120.29	9.845%	$132.1326	$132.13	$132.15	$132.10
Purchase #3	$193.48	6.783%	$206.6037	$206.60	$206.60	$206.60
Purchase #4	$95.82	9.584%	$105.0034	$105.00	$105.00	$105.00
Purchase #5	$221.81	10.195%	$244.4235	$244.42	$244.40	$244.40
Purchase #6	$112.80	12.164%	$126.521	$126.52	$126.50	$126.50
Purchase #7	$103.94	5.558%	$109.717	$109.72	$109.70	$109.70
7 purchase totals =	$976.39		$1,060.4898	$1,060.48	$1,060.45	$1,060.40