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	$92.71	13.555%	$105.2768	$105.28	$105.30	$105.30
Purchase #2	$98.45	7.340%	$105.6762	$105.68	$105.70	$105.70
Purchase #3	$209.27	4.248%	$218.1598	$218.16	$218.15	$218.20
Purchase #4	$143.25	3.376%	$148.0861	$148.09	$148.10	$148.10
Purchase #5	$24.66	11.815%	$27.5736	$27.57	$27.55	$27.60
Purchase #6	$68.40	5.486%	$72.1524	$72.15	$72.15	$72.20
Purchase #7	$33.27	4.218%	$34.6733	$34.67	$34.65	$34.70
7 purchase totals =	$670.01		$711.5982	$711.60	$711.60	$711.80