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	$131.62	11.473%	$146.7208	$146.72	$146.70	$146.70
Purchase #2	$46.72	5.799%	$49.4293	$49.43	$49.45	$49.40
Purchase #3	$144.62	4.664%	$151.3651	$151.37	$151.35	$151.40
Purchase #4	$226.26	6.794%	$241.6321	$241.63	$241.65	$241.60
Purchase #5	$33.42	11.429%	$37.2396	$37.24	$37.25	$37.20
Purchase #6	$112.73	12.176%	$126.456	$126.46	$126.45	$126.50
Purchase #7	$164.50	8.613%	$178.6684	$178.67	$178.65	$178.70
7 purchase totals =	$859.87		$931.5113	$931.52	$931.50	$931.50