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	$118.31	13.325%	$134.0748	$134.07	$134.05	$134.10
Purchase #2	$78.72	3.338%	$81.3477	$81.35	$81.35	$81.30
Purchase #3	$160.98	4.630%	$168.4334	$168.43	$168.45	$168.40
Purchase #4	$20.34	7.594%	$21.8846	$21.88	$21.90	$21.90
Purchase #5	$187.58	3.204%	$193.5901	$193.59	$193.60	$193.60
Purchase #6	$16.82	13.532%	$19.0961	$19.10	$19.10	$19.10
Purchase #7	$82.56	10.173%	$90.9588	$90.96	$90.95	$91.00
7 purchase totals =	$665.31		$709.3855	$709.38	$709.40	$709.40