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	$43.77	10.140%	$48.2083	$48.21	$48.20	$48.20
Purchase #2	$188.44	9.491%	$206.3248	$206.32	$206.30	$206.30
Purchase #3	$68.43	6.103%	$72.6063	$72.61	$72.60	$72.60
Purchase #4	$17.84	10.373%	$19.6905	$19.69	$19.70	$19.70
Purchase #5	$18.49	6.650%	$19.7196	$19.72	$19.70	$19.70
Purchase #6	$91.93	9.372%	$100.5457	$100.55	$100.55	$100.50
Purchase #7	$136.60	13.467%	$154.9959	$155.00	$155.00	$155.00
7 purchase totals =	$565.50		$622.0911	$622.10	$622.05	$622.00