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	$36.46	8.188%	$39.4453	$39.45	$39.45	$39.40
Purchase #2	$84.58	13.203%	$95.7471	$95.75	$95.75	$95.70
Purchase #3	$166.37	3.783%	$172.6638	$172.66	$172.65	$172.70
Purchase #4	$82.95	13.644%	$94.2677	$94.27	$94.25	$94.30
Purchase #5	$35.98	7.247%	$38.5875	$38.59	$38.60	$38.60
Purchase #6	$127.70	6.767%	$136.3415	$136.34	$136.35	$136.30
Purchase #7	$10.89	4.592%	$11.3901	$11.39	$11.40	$11.40
7 purchase totals =	$544.93		$588.4430	$588.45	$588.45	$588.40