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	$87.63	3.472%	$90.6725	$90.67	$90.65	$90.70
Purchase #2	$72.35	8.365%	$78.4021	$78.40	$78.40	$78.40
Purchase #3	$242.61	6.186%	$257.6179	$257.62	$257.60	$257.60
Purchase #4	$187.46	11.457%	$208.9373	$208.94	$208.95	$208.90
Purchase #5	$74.87	9.298%	$81.8314	$81.83	$81.85	$81.80
Purchase #6	$100.45	7.437%	$107.9205	$107.92	$107.90	$107.90
Purchase #7	$91.57	12.650%	$103.1536	$103.15	$103.15	$103.20
7 purchase totals =	$856.94		$928.5353	$928.53	$928.50	$928.50