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	$99.92	5.725%	$105.6404	$105.64	$105.65	$105.60
Purchase #2	$14.66	6.162%	$15.5633	$15.56	$15.55	$15.60
Purchase #3	$20.25	7.652%	$21.7995	$21.80	$21.80	$21.80
Purchase #4	$101.88	3.637%	$105.5854	$105.59	$105.60	$105.60
Purchase #5	$161.46	13.707%	$183.5913	$183.59	$183.60	$183.60
Purchase #6	$97.71	13.677%	$111.0738	$111.07	$111.05	$111.10
Purchase #7	$205.86	8.503%	$223.3643	$223.36	$223.35	$223.40
7 purchase totals =	$701.74		$766.6180	$766.61	$766.60	$766.70