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	$151.69	9.654%	$166.3342	$166.33	$166.35	$166.30
Purchase #2	$183.95	8.631%	$199.8267	$199.83	$199.85	$199.80
Purchase #3	$80.65	11.379%	$89.8272	$89.83	$89.85	$89.80
Purchase #4	$67.76	4.226%	$70.6235	$70.62	$70.60	$70.60
Purchase #5	$221.45	10.116%	$243.8519	$243.85	$243.85	$243.90
Purchase #6	$140.41	12.845%	$158.4457	$158.45	$158.45	$158.40
Purchase #7	$32.32	5.146%	$33.9832	$33.98	$34.00	$34.00
7 purchase totals =	$878.23		$962.8924	$962.89	$962.95	$962.80