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	$43.90	8.189%	$47.495	$47.50	$47.50	$47.50
Purchase #2	$240.40	6.387%	$255.7543	$255.75	$255.75	$255.80
Purchase #3	$75.29	10.594%	$83.2662	$83.27	$83.25	$83.30
Purchase #4	$117.25	7.741%	$126.3263	$126.33	$126.35	$126.30
Purchase #5	$156.86	11.161%	$174.3671	$174.37	$174.35	$174.40
Purchase #6	$116.93	12.619%	$131.6854	$131.69	$131.70	$131.70
Purchase #7	$46.66	7.443%	$50.1329	$50.13	$50.15	$50.10
7 purchase totals =	$797.29		$869.0272	$869.04	$869.05	$869.10