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	$61.38	5.736%	$64.9008	$64.90	$64.90	$64.90
Purchase #2	$14.78	3.318%	$15.2704	$15.27	$15.25	$15.30
Purchase #3	$29.92	5.431%	$31.545	$31.55	$31.55	$31.50
Purchase #4	$100.38	13.314%	$113.7446	$113.74	$113.75	$113.70
Purchase #5	$90.48	11.203%	$100.6165	$100.62	$100.60	$100.60
Purchase #6	$152.27	8.863%	$165.7657	$165.77	$165.75	$165.80
Purchase #7	$121.32	11.123%	$134.8144	$134.81	$134.80	$134.80
7 purchase totals =	$570.53		$626.6574	$626.66	$626.60	$626.60