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	$117.52	12.178%	$131.8316	$131.83	$131.85	$131.80
Purchase #2	$59.92	12.868%	$67.6305	$67.63	$67.65	$67.60
Purchase #3	$144.27	9.372%	$157.791	$157.79	$157.80	$157.80
Purchase #4	$109.64	8.818%	$119.3081	$119.31	$119.30	$119.30
Purchase #5	$95.60	8.766%	$103.9803	$103.98	$104.00	$104.00
Purchase #6	$248.94	3.676%	$258.091	$258.09	$258.10	$258.10
Purchase #7	$169.53	3.108%	$174.799	$174.80	$174.80	$174.80
7 purchase totals =	$945.42		$1,013.4315	$1,013.43	$1,013.50	$1,013.40