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	$131.47	9.857%	$144.429	$144.43	$144.45	$144.40
Purchase #2	$240.84	5.684%	$254.5293	$254.53	$254.55	$254.50
Purchase #3	$118.55	8.634%	$128.7856	$128.79	$128.80	$128.80
Purchase #4	$137.42	8.369%	$148.9207	$148.92	$148.90	$148.90
Purchase #5	$90.88	4.726%	$95.175	$95.18	$95.20	$95.20
Purchase #6	$31.72	4.230%	$33.0618	$33.06	$33.05	$33.10
Purchase #7	$119.54	10.742%	$132.381	$132.38	$132.40	$132.40
7 purchase totals =	$870.42		$937.2824	$937.29	$937.35	$937.30