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	$20.65	9.486%	$22.6089	$22.61	$22.60	$22.60
Purchase #2	$221.67	7.163%	$237.5482	$237.55	$237.55	$237.50
Purchase #3	$132.27	8.724%	$143.8092	$143.81	$143.80	$143.80
Purchase #4	$148.37	6.858%	$158.5452	$158.55	$158.55	$158.50
Purchase #5	$242.32	9.475%	$265.2798	$265.28	$265.30	$265.30
Purchase #6	$79.37	3.747%	$82.344	$82.34	$82.35	$82.30
Purchase #7	$139.65	8.533%	$151.5663	$151.57	$151.55	$151.60
7 purchase totals =	$984.30		$1,061.7016	$1,061.71	$1,061.70	$1,061.60