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	$129.42	9.613%	$141.8611	$141.86	$141.85	$141.90
Purchase #2	$190.66	4.586%	$199.4037	$199.40	$199.40	$199.40
Purchase #3	$59.97	4.191%	$62.4833	$62.48	$62.50	$62.50
Purchase #4	$106.45	3.242%	$109.9011	$109.90	$109.90	$109.90
Purchase #5	$83.81	6.256%	$89.0532	$89.05	$89.05	$89.10
Purchase #6	$143.63	7.365%	$154.2083	$154.21	$154.20	$154.20
Purchase #7	$146.51	8.847%	$159.4717	$159.47	$159.45	$159.50
7 purchase totals =	$860.45		$916.3824	$916.37	$916.35	$916.50