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	$200.41	13.482%	$227.4293	$227.43	$227.45	$227.40
Purchase #2	$6.70	11.153%	$7.4473	$7.45	$7.45	$7.40
Purchase #3	$223.56	13.677%	$254.1363	$254.14	$254.15	$254.10
Purchase #4	$46.45	13.390%	$52.6697	$52.67	$52.65	$52.70
Purchase #5	$127.79	7.325%	$137.1506	$137.15	$137.15	$137.20
Purchase #6	$171.91	9.139%	$187.6209	$187.62	$187.60	$187.60
Purchase #7	$94.26	9.361%	$103.0837	$103.08	$103.10	$103.10
7 purchase totals =	$871.08		$969.5378	$969.54	$969.55	$969.50