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	$240.52	7.617%	$258.8404	$258.84	$258.85	$258.80
Purchase #2	$50.91	7.461%	$54.7084	$54.71	$54.70	$54.70
Purchase #3	$34.75	10.725%	$38.4769	$38.48	$38.50	$38.50
Purchase #4	$139.82	7.667%	$150.54	$150.54	$150.55	$150.50
Purchase #5	$174.64	13.222%	$197.7309	$197.73	$197.75	$197.70
Purchase #6	$177.58	6.104%	$188.4195	$188.42	$188.40	$188.40
Purchase #7	$247.48	13.105%	$279.9123	$279.91	$279.90	$279.90
7 purchase totals =	$1,065.70		$1,168.6284	$1,168.63	$1,168.65	$1,168.50