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	$199.61	10.106%	$219.7826	$219.78	$219.80	$219.80
Purchase #2	$40.38	6.295%	$42.9219	$42.92	$42.90	$42.90
Purchase #3	$169.42	4.256%	$176.6305	$176.63	$176.65	$176.60
Purchase #4	$49.51	4.868%	$51.9201	$51.92	$51.90	$51.90
Purchase #5	$249.90	3.467%	$258.564	$258.56	$258.55	$258.60
Purchase #6	$104.31	11.769%	$116.5862	$116.59	$116.60	$116.60
Purchase #7	$77.39	9.379%	$84.6484	$84.65	$84.65	$84.60
7 purchase totals =	$890.52		$951.0537	$951.05	$951.05	$951.00