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	$32.28	11.225%	$35.9034	$35.90	$35.90	$35.90
Purchase #2	$24.46	11.772%	$27.3394	$27.34	$27.35	$27.30
Purchase #3	$71.41	8.599%	$77.5505	$77.55	$77.55	$77.60
Purchase #4	$116.78	8.702%	$126.9422	$126.94	$126.95	$126.90
Purchase #5	$29.29	8.571%	$31.8004	$31.80	$31.80	$31.80
Purchase #6	$214.66	3.843%	$222.9094	$222.91	$222.90	$222.90
Purchase #7	$51.84	6.522%	$55.221	$55.22	$55.20	$55.20
7 purchase totals =	$540.72		$577.6663	$577.66	$577.65	$577.60