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	$50.88	11.195%	$56.576	$56.58	$56.60	$56.60
Purchase #2	$53.56	7.275%	$57.4565	$57.46	$57.45	$57.50
Purchase #3	$236.49	4.175%	$246.3635	$246.36	$246.35	$246.40
Purchase #4	$42.30	13.288%	$47.9208	$47.92	$47.90	$47.90
Purchase #5	$209.26	6.379%	$222.6087	$222.61	$222.60	$222.60
Purchase #6	$153.26	12.340%	$172.1723	$172.17	$172.15	$172.20
Purchase #7	$41.53	3.494%	$42.9811	$42.98	$43.00	$43.00
7 purchase totals =	$787.28		$846.0789	$846.08	$846.05	$846.20