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	$74.77	9.854%	$82.1378	$82.14	$82.15	$82.10
Purchase #2	$213.50	10.590%	$236.1097	$236.11	$236.10	$236.10
Purchase #3	$194.49	10.343%	$214.6061	$214.61	$214.60	$214.60
Purchase #4	$126.76	10.339%	$139.8657	$139.87	$139.85	$139.90
Purchase #5	$199.96	13.837%	$227.6285	$227.63	$227.65	$227.60
Purchase #6	$49.41	3.296%	$51.0386	$51.04	$51.05	$51.00
Purchase #7	$114.82	7.208%	$123.0962	$123.10	$123.10	$123.10
7 purchase totals =	$973.71		$1,074.4826	$1,074.50	$1,074.50	$1,074.40