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	$203.69	5.133%	$214.1454	$214.15	$214.15	$214.10
Purchase #2	$212.31	7.513%	$228.2609	$228.26	$228.25	$228.30
Purchase #3	$120.38	8.846%	$131.0288	$131.03	$131.05	$131.00
Purchase #4	$70.39	11.238%	$78.3004	$78.30	$78.30	$78.30
Purchase #5	$19.39	13.159%	$21.9415	$21.94	$21.95	$21.90
Purchase #6	$231.94	5.559%	$244.8335	$244.83	$244.85	$244.80
Purchase #7	$40.27	13.692%	$45.7838	$45.78	$45.80	$45.80
7 purchase totals =	$898.37		$964.2943	$964.29	$964.35	$964.20