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	$102.85	8.549%	$111.6426	$111.64	$111.65	$111.60
Purchase #2	$137.96	3.207%	$142.3844	$142.38	$142.40	$142.40
Purchase #3	$66.48	4.791%	$69.6651	$69.67	$69.65	$69.70
Purchase #4	$178.42	11.604%	$199.1239	$199.12	$199.10	$199.10
Purchase #5	$6.84	10.491%	$7.5576	$7.56	$7.55	$7.60
Purchase #6	$154.72	8.558%	$167.9609	$167.96	$167.95	$168.00
Purchase #7	$52.76	5.390%	$55.6038	$55.60	$55.60	$55.60
7 purchase totals =	$700.03		$753.9383	$753.93	$753.90	$754.00