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	$111.92	11.249%	$124.5099	$124.51	$124.50	$124.50
Purchase #2	$72.67	7.455%	$78.0875	$78.09	$78.10	$78.10
Purchase #3	$30.85	13.274%	$34.945	$34.95	$34.95	$34.90
Purchase #4	$157.98	13.771%	$179.7354	$179.74	$179.75	$179.70
Purchase #5	$179.78	7.690%	$193.6051	$193.61	$193.60	$193.60
Purchase #6	$116.84	8.724%	$127.0331	$127.03	$127.05	$127.00
Purchase #7	$157.33	11.159%	$174.8865	$174.89	$174.90	$174.90
7 purchase totals =	$827.37		$912.8025	$912.82	$912.85	$912.70