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	$138.65	8.625%	$150.6086	$150.61	$150.60	$150.60
Purchase #2	$119.51	4.456%	$124.8354	$124.84	$124.85	$124.80
Purchase #3	$141.46	12.784%	$159.5442	$159.54	$159.55	$159.50
Purchase #4	$9.89	8.724%	$10.7528	$10.75	$10.75	$10.80
Purchase #5	$234.81	12.373%	$263.863	$263.86	$263.85	$263.90
Purchase #6	$233.90	9.692%	$256.5696	$256.57	$256.55	$256.60
Purchase #7	$104.78	12.462%	$117.8377	$117.84	$117.85	$117.80
7 purchase totals =	$983.00		$1,084.0113	$1,084.01	$1,084.00	$1,084.00