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	$37.81	8.636%	$41.0753	$41.08	$41.10	$41.10
Purchase #2	$33.32	10.774%	$36.9099	$36.91	$36.90	$36.90
Purchase #3	$104.61	7.397%	$112.348	$112.35	$112.35	$112.30
Purchase #4	$40.83	6.751%	$43.5864	$43.59	$43.60	$43.60
Purchase #5	$172.52	9.542%	$188.9819	$188.98	$189.00	$189.00
Purchase #6	$28.93	6.152%	$30.7098	$30.71	$30.70	$30.70
Purchase #7	$37.96	6.602%	$40.4661	$40.47	$40.45	$40.50
7 purchase totals =	$455.98		$494.0774	$494.09	$494.10	$494.10