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	$170.45	11.724%	$190.4336	$190.43	$190.45	$190.40
Purchase #2	$172.93	13.505%	$196.2842	$196.28	$196.30	$196.30
Purchase #3	$143.35	10.291%	$158.1021	$158.10	$158.10	$158.10
Purchase #4	$5.75	6.557%	$6.127	$6.13	$6.15	$6.10
Purchase #5	$14.75	3.281%	$15.2339	$15.23	$15.25	$15.20
Purchase #6	$245.69	4.791%	$257.461	$257.46	$257.45	$257.50
Purchase #7	$115.50	4.161%	$120.306	$120.31	$120.30	$120.30
7 purchase totals =	$868.42		$943.9478	$943.94	$944.00	$943.90