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	$133.85	9.339%	$146.3503	$146.35	$146.35	$146.40
Purchase #2	$109.72	6.606%	$116.9681	$116.97	$116.95	$117.00
Purchase #3	$184.66	7.723%	$198.9213	$198.92	$198.90	$198.90
Purchase #4	$162.43	6.283%	$172.6355	$172.64	$172.65	$172.60
Purchase #5	$188.36	12.189%	$211.3192	$211.32	$211.30	$211.30
Purchase #6	$200.52	13.647%	$227.885	$227.89	$227.90	$227.90
Purchase #7	$22.25	7.123%	$23.8349	$23.83	$23.85	$23.80
7 purchase totals =	$1,001.79		$1,097.9143	$1,097.92	$1,097.90	$1,097.90