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	$105.73	9.582%	$115.861	$115.86	$115.85	$115.90
Purchase #2	$80.96	3.447%	$83.7507	$83.75	$83.75	$83.80
Purchase #3	$107.70	3.548%	$111.5212	$111.52	$111.50	$111.50
Purchase #4	$235.87	9.629%	$258.5819	$258.58	$258.60	$258.60
Purchase #5	$20.82	10.164%	$22.9361	$22.94	$22.95	$22.90
Purchase #6	$208.48	4.296%	$217.4363	$217.44	$217.45	$217.40
Purchase #7	$232.44	11.757%	$259.768	$259.77	$259.75	$259.80
7 purchase totals =	$992.00		$1,069.8552	$1,069.86	$1,069.85	$1,069.90