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	$109.80	9.552%	$120.2881	$120.29	$120.30	$120.30
Purchase #2	$122.62	7.158%	$131.3971	$131.40	$131.40	$131.40
Purchase #3	$20.60	5.738%	$21.782	$21.78	$21.80	$21.80
Purchase #4	$78.49	9.442%	$85.901	$85.90	$85.90	$85.90
Purchase #5	$223.68	10.807%	$247.8531	$247.85	$247.85	$247.90
Purchase #6	$188.61	5.526%	$199.0326	$199.03	$199.05	$199.00
Purchase #7	$24.57	11.592%	$27.4182	$27.42	$27.40	$27.40
7 purchase totals =	$768.37		$833.6721	$833.67	$833.70	$833.70