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	$117.63	8.733%	$127.9026	$127.90	$127.90	$127.90
Purchase #2	$35.95	9.166%	$39.2452	$39.25	$39.25	$39.20
Purchase #3	$39.38	6.389%	$41.896	$41.90	$41.90	$41.90
Purchase #4	$161.86	13.222%	$183.2611	$183.26	$183.25	$183.30
Purchase #5	$78.46	5.434%	$82.7235	$82.72	$82.70	$82.70
Purchase #6	$14.80	4.180%	$15.4186	$15.42	$15.40	$15.40
Purchase #7	$87.39	5.453%	$92.1554	$92.16	$92.15	$92.20
7 purchase totals =	$535.47		$582.6024	$582.61	$582.55	$582.60