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	$127.42	4.681%	$133.3845	$133.38	$133.40	$133.40
Purchase #2	$117.38	12.186%	$131.6839	$131.68	$131.70	$131.70
Purchase #3	$199.63	11.584%	$222.7551	$222.76	$222.75	$222.80
Purchase #4	$245.89	5.241%	$258.7771	$258.78	$258.80	$258.80
Purchase #5	$96.60	7.171%	$103.5272	$103.53	$103.55	$103.50
Purchase #6	$76.65	13.834%	$87.2538	$87.25	$87.25	$87.30
Purchase #7	$175.48	3.440%	$181.5165	$181.52	$181.50	$181.50
7 purchase totals =	$1,039.05		$1,118.8981	$1,118.90	$1,118.95	$1,119.00