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	$32.37	7.657%	$34.8486	$34.85	$34.85	$34.80
Purchase #2	$12.78	4.631%	$13.3718	$13.37	$13.35	$13.40
Purchase #3	$194.95	5.610%	$205.8867	$205.89	$205.90	$205.90
Purchase #4	$80.76	12.418%	$90.7888	$90.79	$90.80	$90.80
Purchase #5	$72.68	4.286%	$75.7951	$75.80	$75.80	$75.80
Purchase #6	$131.77	4.433%	$137.6114	$137.61	$137.60	$137.60
Purchase #7	$97.75	4.664%	$102.3091	$102.31	$102.30	$102.30
7 purchase totals =	$623.06		$660.6115	$660.62	$660.60	$660.60