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	$222.90	7.334%	$239.2475	$239.25	$239.25	$239.20
Purchase #2	$54.98	5.237%	$57.8593	$57.86	$57.85	$57.90
Purchase #3	$244.66	11.104%	$271.827	$271.83	$271.85	$271.80
Purchase #4	$51.60	11.119%	$57.3374	$57.34	$57.35	$57.30
Purchase #5	$218.27	5.429%	$230.1199	$230.12	$230.10	$230.10
Purchase #6	$194.28	10.180%	$214.0577	$214.06	$214.05	$214.10
Purchase #7	$94.28	6.716%	$100.6118	$100.61	$100.60	$100.60
7 purchase totals =	$1,080.97		$1,171.0606	$1,171.07	$1,171.05	$1,171.00