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	$59.73	6.455%	$63.5856	$63.59	$63.60	$63.60
Purchase #2	$55.50	5.859%	$58.7517	$58.75	$58.75	$58.80
Purchase #3	$156.68	3.290%	$161.8348	$161.83	$161.85	$161.80
Purchase #4	$29.94	9.603%	$32.8151	$32.82	$32.80	$32.80
Purchase #5	$151.88	13.260%	$172.0193	$172.02	$172.00	$172.00
Purchase #6	$147.92	12.628%	$166.5993	$166.60	$166.60	$166.60
Purchase #7	$46.87	4.326%	$48.8976	$48.90	$48.90	$48.90
7 purchase totals =	$648.52		$704.5034	$704.51	$704.50	$704.50