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	$149.79	12.195%	$168.0569	$168.06	$168.05	$168.10
Purchase #2	$12.45	8.477%	$13.5054	$13.51	$13.50	$13.50
Purchase #3	$87.52	3.552%	$90.6287	$90.63	$90.65	$90.60
Purchase #4	$121.98	7.497%	$131.1248	$131.12	$131.10	$131.10
Purchase #5	$209.44	8.456%	$227.1502	$227.15	$227.15	$227.20
Purchase #6	$103.62	6.574%	$110.432	$110.43	$110.45	$110.40
Purchase #7	$120.68	6.748%	$128.8235	$128.82	$128.80	$128.80
7 purchase totals =	$805.48		$869.7215	$869.72	$869.70	$869.70