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	$103.89	13.651%	$118.072	$118.07	$118.05	$118.10
Purchase #2	$90.97	3.143%	$93.8292	$93.83	$93.85	$93.80
Purchase #3	$133.49	6.724%	$142.4659	$142.47	$142.45	$142.50
Purchase #4	$241.61	6.212%	$256.6188	$256.62	$256.60	$256.60
Purchase #5	$47.56	10.320%	$52.4682	$52.47	$52.45	$52.50
Purchase #6	$155.66	4.163%	$162.1401	$162.14	$162.15	$162.10
Purchase #7	$191.26	7.217%	$205.0632	$205.06	$205.05	$205.10
7 purchase totals =	$964.44		$1,030.6574	$1,030.66	$1,030.60	$1,030.70