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	$30.58	3.270%	$31.58	$31.58	$31.60	$31.60
Purchase #2	$214.95	5.749%	$227.3075	$227.31	$227.30	$227.30
Purchase #3	$101.83	10.587%	$112.6107	$112.61	$112.60	$112.60
Purchase #4	$36.35	10.194%	$40.0555	$40.06	$40.05	$40.10
Purchase #5	$44.88	3.610%	$46.5002	$46.50	$46.50	$46.50
Purchase #6	$222.74	7.213%	$238.8062	$238.81	$238.80	$238.80
Purchase #7	$12.39	13.393%	$14.0494	$14.05	$14.05	$14.00
7 purchase totals =	$663.72		$710.9095	$710.92	$710.90	$710.90