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	$207.39	3.329%	$214.294	$214.29	$214.30	$214.30
Purchase #2	$215.32	11.478%	$240.0344	$240.03	$240.05	$240.00
Purchase #3	$117.92	7.341%	$126.5765	$126.58	$126.60	$126.60
Purchase #4	$49.94	7.372%	$53.6216	$53.62	$53.60	$53.60
Purchase #5	$78.42	9.594%	$85.9436	$85.94	$85.95	$85.90
Purchase #6	$136.81	4.316%	$142.7147	$142.71	$142.70	$142.70
Purchase #7	$132.27	12.517%	$148.8262	$148.83	$148.85	$148.80
7 purchase totals =	$938.07		$1,012.0110	$1,012.00	$1,012.05	$1,011.90