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	$197.72	9.481%	$216.4658	$216.47	$216.45	$216.50
Purchase #2	$189.93	13.222%	$215.0425	$215.04	$215.05	$215.00
Purchase #3	$235.55	13.256%	$266.7745	$266.77	$266.75	$266.80
Purchase #4	$49.89	9.520%	$54.6395	$54.64	$54.65	$54.60
Purchase #5	$241.72	9.808%	$265.4279	$265.43	$265.45	$265.40
Purchase #6	$76.70	7.592%	$82.5231	$82.52	$82.50	$82.50
Purchase #7	$15.69	11.619%	$17.513	$17.51	$17.50	$17.50
7 purchase totals =	$1,007.20		$1,118.3863	$1,118.38	$1,118.35	$1,118.30