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	$235.27	8.532%	$255.3432	$255.34	$255.35	$255.30
Purchase #2	$193.55	11.152%	$215.1347	$215.13	$215.15	$215.10
Purchase #3	$9.58	12.867%	$10.8127	$10.81	$10.80	$10.80
Purchase #4	$166.98	13.795%	$190.0149	$190.01	$190.00	$190.00
Purchase #5	$53.58	11.212%	$59.5874	$59.59	$59.60	$59.60
Purchase #6	$138.87	3.545%	$143.7929	$143.79	$143.80	$143.80
Purchase #7	$223.35	11.800%	$249.7053	$249.71	$249.70	$249.70
7 purchase totals =	$1,021.18		$1,124.3911	$1,124.38	$1,124.40	$1,124.30