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	$244.86	4.749%	$256.4884	$256.49	$256.50	$256.50
Purchase #2	$212.92	9.298%	$232.7173	$232.72	$232.70	$232.70
Purchase #3	$197.55	11.397%	$220.0648	$220.06	$220.05	$220.10
Purchase #4	$66.83	8.218%	$72.3221	$72.32	$72.30	$72.30
Purchase #5	$164.79	3.321%	$170.2627	$170.26	$170.25	$170.30
Purchase #6	$35.92	11.579%	$40.0792	$40.08	$40.10	$40.10
Purchase #7	$103.63	13.503%	$117.6232	$117.62	$117.60	$117.60
7 purchase totals =	$1,026.50		$1,109.5577	$1,109.55	$1,109.50	$1,109.60