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	$31.52	6.324%	$33.5133	$33.51	$33.50	$33.50
Purchase #2	$63.77	4.234%	$66.47	$66.47	$66.45	$66.50
Purchase #3	$246.40	3.702%	$255.5217	$255.52	$255.50	$255.50
Purchase #4	$183.82	13.658%	$208.9261	$208.93	$208.95	$208.90
Purchase #5	$244.58	4.376%	$255.2828	$255.28	$255.30	$255.30
Purchase #6	$228.28	13.238%	$258.4997	$258.50	$258.50	$258.50
Purchase #7	$180.68	9.795%	$198.3776	$198.38	$198.40	$198.40
7 purchase totals =	$1,179.05		$1,276.5912	$1,276.59	$1,276.60	$1,276.60