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	$95.42	5.389%	$100.5622	$100.56	$100.55	$100.60
Purchase #2	$20.55	5.667%	$21.7146	$21.71	$21.70	$21.70
Purchase #3	$132.26	5.162%	$139.0873	$139.09	$139.10	$139.10
Purchase #4	$58.95	11.740%	$65.8707	$65.87	$65.85	$65.90
Purchase #5	$210.33	8.182%	$227.5392	$227.54	$227.55	$227.50
Purchase #6	$206.77	12.766%	$233.1663	$233.17	$233.15	$233.20
Purchase #7	$199.31	7.371%	$214.0011	$214.00	$214.00	$214.00
7 purchase totals =	$923.59		$1,001.9414	$1,001.94	$1,001.90	$1,002.00