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	$160.86	6.304%	$171.0006	$171.00	$171.00	$171.00
Purchase #2	$74.72	7.763%	$80.5205	$80.52	$80.50	$80.50
Purchase #3	$82.61	10.804%	$91.5352	$91.54	$91.55	$91.50
Purchase #4	$111.76	5.836%	$118.2823	$118.28	$118.30	$118.30
Purchase #5	$38.47	6.490%	$40.9667	$40.97	$40.95	$41.00
Purchase #6	$212.45	10.393%	$234.5299	$234.53	$234.55	$234.50
Purchase #7	$202.82	11.312%	$225.763	$225.76	$225.75	$225.80
7 purchase totals =	$883.69		$962.5982	$962.60	$962.60	$962.60