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	$239.28	6.733%	$255.3907	$255.39	$255.40	$255.40
Purchase #2	$149.63	9.424%	$163.7311	$163.73	$163.75	$163.70
Purchase #3	$66.27	8.705%	$72.0388	$72.04	$72.05	$72.00
Purchase #4	$67.94	3.717%	$70.4653	$70.47	$70.45	$70.50
Purchase #5	$29.94	11.478%	$33.3765	$33.38	$33.40	$33.40
Purchase #6	$242.88	5.363%	$255.9057	$255.91	$255.90	$255.90
Purchase #7	$241.80	9.758%	$265.3948	$265.39	$265.40	$265.40
7 purchase totals =	$1,037.74		$1,116.3029	$1,116.31	$1,116.35	$1,116.30