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	$91.42	4.638%	$95.6601	$95.66	$95.65	$95.70
Purchase #2	$144.25	7.191%	$154.623	$154.62	$154.60	$154.60
Purchase #3	$38.61	10.309%	$42.5903	$42.59	$42.60	$42.60
Purchase #4	$140.96	7.702%	$151.8167	$151.82	$151.80	$151.80
Purchase #5	$63.27	13.462%	$71.7874	$71.79	$71.80	$71.80
Purchase #6	$18.28	8.410%	$19.8173	$19.82	$19.80	$19.80
Purchase #7	$51.76	9.202%	$56.523	$56.52	$56.50	$56.50
7 purchase totals =	$548.55		$592.8178	$592.82	$592.75	$592.80