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	$239.72	3.522%	$248.1629	$248.16	$248.15	$248.20
Purchase #2	$76.83	10.802%	$85.1292	$85.13	$85.15	$85.10
Purchase #3	$40.76	6.806%	$43.5341	$43.53	$43.55	$43.50
Purchase #4	$248.49	3.349%	$256.8119	$256.81	$256.80	$256.80
Purchase #5	$121.34	10.314%	$133.855	$133.86	$133.85	$133.90
Purchase #6	$107.69	13.834%	$122.5878	$122.59	$122.60	$122.60
Purchase #7	$135.49	4.476%	$141.5545	$141.55	$141.55	$141.60
7 purchase totals =	$970.32		$1,031.6354	$1,031.63	$1,031.65	$1,031.70