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	$134.75	12.407%	$151.4684	$151.47	$151.45	$151.50
Purchase #2	$212.81	6.441%	$226.5171	$226.52	$226.50	$226.50
Purchase #3	$10.55	11.471%	$11.7602	$11.76	$11.75	$11.80
Purchase #4	$19.55	7.443%	$21.0051	$21.01	$21.00	$21.00
Purchase #5	$200.44	13.545%	$227.5896	$227.59	$227.60	$227.60
Purchase #6	$153.86	9.523%	$168.5121	$168.51	$168.50	$168.50
Purchase #7	$42.82	5.732%	$45.2744	$45.27	$45.25	$45.30
7 purchase totals =	$774.78		$852.1269	$852.13	$852.05	$852.20