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	$217.88	6.105%	$231.1816	$231.18	$231.20	$231.20
Purchase #2	$90.32	11.246%	$100.4774	$100.48	$100.50	$100.50
Purchase #3	$85.76	7.242%	$91.9707	$91.97	$91.95	$92.00
Purchase #4	$175.28	13.585%	$199.0918	$199.09	$199.10	$199.10
Purchase #5	$45.49	6.558%	$48.4732	$48.47	$48.45	$48.50
Purchase #6	$249.51	9.318%	$272.7593	$272.76	$272.75	$272.80
Purchase #7	$42.74	13.630%	$48.5655	$48.57	$48.55	$48.60
7 purchase totals =	$906.98		$992.5195	$992.52	$992.50	$992.70