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	$104.84	11.287%	$116.6733	$116.67	$116.65	$116.70
Purchase #2	$190.80	4.151%	$198.7201	$198.72	$198.70	$198.70
Purchase #3	$52.83	11.859%	$59.0951	$59.10	$59.10	$59.10
Purchase #4	$221.51	9.289%	$242.0861	$242.09	$242.10	$242.10
Purchase #5	$141.29	9.302%	$154.4328	$154.43	$154.45	$154.40
Purchase #6	$204.32	8.333%	$221.346	$221.35	$221.35	$221.30
Purchase #7	$40.85	13.705%	$46.4485	$46.45	$46.45	$46.40
7 purchase totals =	$956.44		$1,038.8019	$1,038.81	$1,038.80	$1,038.70