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	$86.30	11.523%	$96.2443	$96.24	$96.25	$96.20
Purchase #2	$131.27	5.476%	$138.4583	$138.46	$138.45	$138.50
Purchase #3	$50.62	8.164%	$54.7526	$54.75	$54.75	$54.80
Purchase #4	$111.96	4.520%	$117.0206	$117.02	$117.00	$117.00
Purchase #5	$34.59	9.438%	$37.8546	$37.85	$37.85	$37.90
Purchase #6	$172.37	4.733%	$180.5283	$180.53	$180.55	$180.50
Purchase #7	$59.59	3.719%	$61.8062	$61.81	$61.80	$61.80
7 purchase totals =	$646.70		$686.6649	$686.66	$686.65	$686.70