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	$33.88	3.834%	$35.179	$35.18	$35.20	$35.20
Purchase #2	$26.53	12.316%	$29.7974	$29.80	$29.80	$29.80
Purchase #3	$15.89	10.224%	$17.5146	$17.51	$17.50	$17.50
Purchase #4	$97.31	6.223%	$103.3656	$103.37	$103.35	$103.40
Purchase #5	$119.78	9.749%	$131.4574	$131.46	$131.45	$131.50
Purchase #6	$28.78	3.493%	$29.7853	$29.79	$29.80	$29.80
Purchase #7	$109.52	11.874%	$122.5244	$122.52	$122.50	$122.50
7 purchase totals =	$431.69		$469.6237	$469.63	$469.60	$469.70