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	$154.59	13.505%	$175.4674	$175.47	$175.45	$175.50
Purchase #2	$25.42	3.127%	$26.2149	$26.21	$26.20	$26.20
Purchase #3	$158.98	13.184%	$179.9399	$179.94	$179.95	$179.90
Purchase #4	$35.71	12.838%	$40.2944	$40.29	$40.30	$40.30
Purchase #5	$237.45	3.464%	$245.6753	$245.68	$245.70	$245.70
Purchase #6	$87.85	13.676%	$99.8644	$99.86	$99.85	$99.90
Purchase #7	$163.57	5.724%	$172.9327	$172.93	$172.95	$172.90
7 purchase totals =	$863.57		$940.3890	$940.38	$940.40	$940.40