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	$31.41	9.322%	$34.338	$34.34	$34.35	$34.30
Purchase #2	$76.83	8.862%	$83.6387	$83.64	$83.65	$83.60
Purchase #3	$20.86	4.423%	$21.7826	$21.78	$21.80	$21.80
Purchase #4	$199.34	9.371%	$218.0202	$218.02	$218.00	$218.00
Purchase #5	$246.28	13.529%	$279.5992	$279.60	$279.60	$279.60
Purchase #6	$156.85	4.753%	$164.3051	$164.31	$164.30	$164.30
Purchase #7	$150.30	5.675%	$158.8295	$158.83	$158.85	$158.80
7 purchase totals =	$881.87		$960.5133	$960.52	$960.55	$960.40