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	$225.34	13.635%	$256.0651	$256.07	$256.05	$256.10
Purchase #2	$96.29	4.665%	$100.7819	$100.78	$100.80	$100.80
Purchase #3	$124.88	7.413%	$134.1374	$134.14	$134.15	$134.10
Purchase #4	$96.51	5.779%	$102.0873	$102.09	$102.10	$102.10
Purchase #5	$94.59	7.232%	$101.4307	$101.43	$101.45	$101.40
Purchase #6	$163.72	11.778%	$183.0029	$183.00	$183.00	$183.00
Purchase #7	$150.83	9.150%	$164.6309	$164.63	$164.65	$164.60
7 purchase totals =	$952.16		$1,042.1362	$1,042.14	$1,042.20	$1,042.10