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	$226.67	5.385%	$238.8762	$238.88	$238.90	$238.90
Purchase #2	$83.71	6.278%	$88.9653	$88.97	$88.95	$89.00
Purchase #3	$208.89	8.826%	$227.3266	$227.33	$227.35	$227.30
Purchase #4	$42.34	3.314%	$43.7431	$43.74	$43.75	$43.70
Purchase #5	$33.90	7.339%	$36.3879	$36.39	$36.40	$36.40
Purchase #6	$101.53	10.284%	$111.9713	$111.97	$111.95	$112.00
Purchase #7	$112.45	3.806%	$116.7298	$116.73	$116.75	$116.70
7 purchase totals =	$809.49		$864.0002	$864.01	$864.05	$864.00