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	$213.83	13.346%	$242.3678	$242.37	$242.35	$242.40
Purchase #2	$21.99	5.177%	$23.1284	$23.13	$23.15	$23.10
Purchase #3	$167.68	10.725%	$185.6637	$185.66	$185.65	$185.70
Purchase #4	$17.64	4.874%	$18.4998	$18.50	$18.50	$18.50
Purchase #5	$103.80	8.450%	$112.5711	$112.57	$112.55	$112.60
Purchase #6	$100.95	10.771%	$111.8233	$111.82	$111.80	$111.80
Purchase #7	$194.92	9.553%	$213.5407	$213.54	$213.55	$213.50
7 purchase totals =	$820.81		$907.5948	$907.59	$907.55	$907.60