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	$64.86	12.259%	$72.8112	$72.81	$72.80	$72.80
Purchase #2	$45.32	11.660%	$50.6043	$50.60	$50.60	$50.60
Purchase #3	$32.55	4.163%	$33.9051	$33.91	$33.90	$33.90
Purchase #4	$13.85	10.559%	$15.3124	$15.31	$15.30	$15.30
Purchase #5	$153.48	4.531%	$160.4342	$160.43	$160.45	$160.40
Purchase #6	$82.49	12.572%	$92.8606	$92.86	$92.85	$92.90
Purchase #7	$48.44	9.533%	$53.0578	$53.06	$53.05	$53.10
7 purchase totals =	$440.99		$478.9856	$478.98	$478.95	$479.00