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	$116.37	9.162%	$127.0318	$127.03	$127.05	$127.00
Purchase #2	$134.49	6.189%	$142.8136	$142.81	$142.80	$142.80
Purchase #3	$6.80	6.841%	$7.2652	$7.27	$7.25	$7.30
Purchase #4	$230.45	11.167%	$256.1844	$256.18	$256.20	$256.20
Purchase #5	$225.76	11.791%	$252.3794	$252.38	$252.40	$252.40
Purchase #6	$84.65	10.838%	$93.8244	$93.82	$93.80	$93.80
Purchase #7	$133.72	12.789%	$150.8215	$150.82	$150.80	$150.80
7 purchase totals =	$932.24		$1,030.3203	$1,030.31	$1,030.30	$1,030.30