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	$209.95	3.360%	$217.0043	$217.00	$217.00	$217.00
Purchase #2	$84.75	9.254%	$92.5928	$92.59	$92.60	$92.60
Purchase #3	$205.34	4.757%	$215.108	$215.11	$215.10	$215.10
Purchase #4	$100.71	10.410%	$111.1939	$111.19	$111.20	$111.20
Purchase #5	$184.38	8.660%	$200.3473	$200.35	$200.35	$200.30
Purchase #6	$28.25	12.866%	$31.8846	$31.88	$31.90	$31.90
Purchase #7	$89.34	5.422%	$94.184	$94.18	$94.20	$94.20
7 purchase totals =	$902.72		$962.3149	$962.30	$962.35	$962.30