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	$204.80	3.587%	$212.1462	$212.15	$212.15	$212.10
Purchase #2	$114.31	8.330%	$123.832	$123.83	$123.85	$123.80
Purchase #3	$126.61	3.743%	$131.349	$131.35	$131.35	$131.30
Purchase #4	$109.57	10.563%	$121.1439	$121.14	$121.15	$121.10
Purchase #5	$144.61	8.537%	$156.9554	$156.96	$156.95	$157.00
Purchase #6	$241.49	6.379%	$256.8946	$256.89	$256.90	$256.90
Purchase #7	$130.35	5.163%	$137.08	$137.08	$137.10	$137.10
7 purchase totals =	$1,071.74		$1,139.4011	$1,139.40	$1,139.45	$1,139.30