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	$61.85	3.241%	$63.8546	$63.85	$63.85	$63.90
Purchase #2	$236.95	11.387%	$263.9315	$263.93	$263.95	$263.90
Purchase #3	$53.59	13.440%	$60.7925	$60.79	$60.80	$60.80
Purchase #4	$55.46	11.286%	$61.7192	$61.72	$61.70	$61.70
Purchase #5	$11.98	7.572%	$12.8871	$12.89	$12.90	$12.90
Purchase #6	$68.72	12.440%	$77.2688	$77.27	$77.25	$77.30
Purchase #7	$250.89	11.314%	$279.2757	$279.28	$279.30	$279.30
7 purchase totals =	$739.44		$819.7294	$819.73	$819.75	$819.80