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	$241.34	10.670%	$267.091	$267.09	$267.10	$267.10
Purchase #2	$86.71	4.341%	$90.4741	$90.47	$90.45	$90.50
Purchase #3	$83.35	8.506%	$90.4398	$90.44	$90.45	$90.40
Purchase #4	$63.49	10.189%	$69.959	$69.96	$69.95	$70.00
Purchase #5	$137.33	9.663%	$150.6002	$150.60	$150.60	$150.60
Purchase #6	$160.53	10.203%	$176.9089	$176.91	$176.90	$176.90
Purchase #7	$90.38	13.319%	$102.4177	$102.42	$102.40	$102.40
7 purchase totals =	$863.13		$947.8907	$947.89	$947.85	$947.90