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	$215.82	11.745%	$241.1681	$241.17	$241.15	$241.20
Purchase #2	$61.35	5.352%	$64.6335	$64.63	$64.65	$64.60
Purchase #3	$195.34	13.660%	$222.0234	$222.02	$222.00	$222.00
Purchase #4	$248.98	9.580%	$272.8323	$272.83	$272.85	$272.80
Purchase #5	$150.79	6.456%	$160.525	$160.53	$160.55	$160.50
Purchase #6	$36.47	12.367%	$40.9802	$40.98	$41.00	$41.00
Purchase #7	$17.80	3.277%	$18.3833	$18.38	$18.40	$18.40
7 purchase totals =	$926.55		$1,020.5458	$1,020.54	$1,020.60	$1,020.50