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	$34.31	4.615%	$35.8934	$35.89	$35.90	$35.90
Purchase #2	$219.47	11.635%	$245.0053	$245.01	$245.00	$245.00
Purchase #3	$34.98	5.526%	$36.913	$36.91	$36.90	$36.90
Purchase #4	$126.69	3.465%	$131.0798	$131.08	$131.10	$131.10
Purchase #5	$166.77	5.808%	$176.456	$176.46	$176.45	$176.50
Purchase #6	$138.43	8.373%	$150.0207	$150.02	$150.00	$150.00
Purchase #7	$142.39	10.501%	$157.3424	$157.34	$157.35	$157.30
7 purchase totals =	$863.04		$932.7106	$932.71	$932.70	$932.70