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	$247.28	3.257%	$255.3339	$255.33	$255.35	$255.30
Purchase #2	$157.57	5.704%	$166.5578	$166.56	$166.55	$166.60
Purchase #3	$30.85	9.647%	$33.8261	$33.83	$33.85	$33.80
Purchase #4	$10.31	12.332%	$11.5814	$11.58	$11.60	$11.60
Purchase #5	$208.35	11.318%	$231.9311	$231.93	$231.95	$231.90
Purchase #6	$177.60	5.675%	$187.6788	$187.68	$187.70	$187.70
Purchase #7	$176.87	5.739%	$187.0206	$187.02	$187.00	$187.00
7 purchase totals =	$1,008.83		$1,073.9297	$1,073.93	$1,074.00	$1,073.90