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	$115.60	9.508%	$126.5912	$126.59	$126.60	$126.60
Purchase #2	$71.62	5.375%	$75.4696	$75.47	$75.45	$75.50
Purchase #3	$117.70	8.330%	$127.5044	$127.50	$127.50	$127.50
Purchase #4	$65.42	9.311%	$71.5113	$71.51	$71.50	$71.50
Purchase #5	$205.67	4.604%	$215.139	$215.14	$215.15	$215.10
Purchase #6	$60.37	5.140%	$63.473	$63.47	$63.45	$63.50
Purchase #7	$199.28	8.205%	$215.6309	$215.63	$215.65	$215.60
7 purchase totals =	$835.66		$895.3194	$895.31	$895.30	$895.30