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	$232.63	9.802%	$255.4324	$255.43	$255.45	$255.40
Purchase #2	$97.84	5.573%	$103.2926	$103.29	$103.30	$103.30
Purchase #3	$37.62	7.548%	$40.4596	$40.46	$40.45	$40.50
Purchase #4	$41.43	5.499%	$43.7082	$43.71	$43.70	$43.70
Purchase #5	$175.25	10.784%	$194.149	$194.15	$194.15	$194.10
Purchase #6	$101.98	13.755%	$116.0073	$116.01	$116.00	$116.00
Purchase #7	$225.70	13.500%	$256.1695	$256.17	$256.15	$256.20
7 purchase totals =	$912.45		$1,009.2186	$1,009.22	$1,009.20	$1,009.20