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	$56.34	9.308%	$61.5841	$61.58	$61.60	$61.60
Purchase #2	$101.94	5.238%	$107.2796	$107.28	$107.30	$107.30
Purchase #3	$14.68	8.244%	$15.8902	$15.89	$15.90	$15.90
Purchase #4	$49.53	13.806%	$56.3681	$56.37	$56.35	$56.40
Purchase #5	$250.51	7.395%	$269.0352	$269.04	$269.05	$269.00
Purchase #6	$115.66	10.543%	$127.854	$127.85	$127.85	$127.90
Purchase #7	$248.47	10.726%	$275.1209	$275.12	$275.10	$275.10
7 purchase totals =	$837.13		$913.1321	$913.13	$913.15	$913.20