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	$62.58	13.439%	$70.9901	$70.99	$71.00	$71.00
Purchase #2	$90.72	4.119%	$94.4568	$94.46	$94.45	$94.50
Purchase #3	$232.38	7.606%	$250.0548	$250.05	$250.05	$250.10
Purchase #4	$10.66	8.690%	$11.5864	$11.59	$11.60	$11.60
Purchase #5	$12.34	8.733%	$13.4177	$13.42	$13.40	$13.40
Purchase #6	$97.65	6.853%	$104.342	$104.34	$104.35	$104.30
Purchase #7	$62.78	3.725%	$65.1186	$65.12	$65.10	$65.10
7 purchase totals =	$569.11		$609.9664	$609.97	$609.95	$610.00