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	$47.85	8.631%	$51.9799	$51.98	$52.00	$52.00
Purchase #2	$236.38	10.677%	$261.6183	$261.62	$261.60	$261.60
Purchase #3	$248.65	4.409%	$259.613	$259.61	$259.60	$259.60
Purchase #4	$54.97	12.395%	$61.7835	$61.78	$61.80	$61.80
Purchase #5	$58.49	9.287%	$63.922	$63.92	$63.90	$63.90
Purchase #6	$180.59	3.874%	$187.5861	$187.59	$187.60	$187.60
Purchase #7	$61.89	5.189%	$65.1015	$65.10	$65.10	$65.10
7 purchase totals =	$888.82		$951.6043	$951.60	$951.60	$951.60