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	$27.51	6.218%	$29.2206	$29.22	$29.20	$29.20
Purchase #2	$143.60	13.163%	$162.5021	$162.50	$162.50	$162.50
Purchase #3	$39.43	6.415%	$41.9594	$41.96	$41.95	$42.00
Purchase #4	$188.27	4.143%	$196.07	$196.07	$196.05	$196.10
Purchase #5	$236.43	4.169%	$246.2868	$246.29	$246.30	$246.30
Purchase #6	$63.62	3.105%	$65.5954	$65.60	$65.60	$65.60
Purchase #7	$126.79	13.509%	$143.9181	$143.92	$143.90	$143.90
7 purchase totals =	$825.65		$885.5524	$885.56	$885.50	$885.60