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	$31.60	4.530%	$33.0315	$33.03	$33.05	$33.00
Purchase #2	$108.40	13.587%	$123.1283	$123.13	$123.15	$123.10
Purchase #3	$111.69	5.136%	$117.4264	$117.43	$117.45	$117.40
Purchase #4	$65.95	10.749%	$73.039	$73.04	$73.05	$73.00
Purchase #5	$89.66	8.357%	$97.1529	$97.15	$97.15	$97.20
Purchase #6	$156.68	3.455%	$162.0933	$162.09	$162.10	$162.10
Purchase #7	$53.60	7.144%	$57.4292	$57.43	$57.45	$57.40
7 purchase totals =	$617.58		$663.3006	$663.30	$663.40	$663.20