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	$213.99	11.437%	$238.464	$238.46	$238.45	$238.50
Purchase #2	$151.27	6.376%	$160.915	$160.92	$160.90	$160.90
Purchase #3	$227.74	5.128%	$239.4185	$239.42	$239.40	$239.40
Purchase #4	$242.64	5.284%	$255.4611	$255.46	$255.45	$255.50
Purchase #5	$14.55	8.677%	$15.8125	$15.81	$15.80	$15.80
Purchase #6	$104.33	7.128%	$111.7666	$111.77	$111.75	$111.80
Purchase #7	$16.62	5.283%	$17.498	$17.50	$17.50	$17.50
7 purchase totals =	$971.14		$1,039.3357	$1,039.34	$1,039.25	$1,039.40