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	$56.45	11.326%	$62.8435	$62.84	$62.85	$62.80
Purchase #2	$232.92	11.454%	$259.5987	$259.60	$259.60	$259.60
Purchase #3	$87.72	13.265%	$99.3561	$99.36	$99.35	$99.40
Purchase #4	$113.74	3.278%	$117.4684	$117.47	$117.45	$117.50
Purchase #5	$230.41	11.689%	$257.3426	$257.34	$257.35	$257.30
Purchase #6	$99.43	11.670%	$111.0335	$111.03	$111.05	$111.00
Purchase #7	$33.70	11.129%	$37.4505	$37.45	$37.45	$37.50
7 purchase totals =	$854.37		$945.0933	$945.09	$945.10	$945.10