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	$143.66	13.178%	$162.5915	$162.59	$162.60	$162.60
Purchase #2	$184.93	12.646%	$208.3162	$208.32	$208.30	$208.30
Purchase #3	$19.64	8.159%	$21.2424	$21.24	$21.25	$21.20
Purchase #4	$88.75	4.389%	$92.6452	$92.65	$92.65	$92.60
Purchase #5	$5.52	7.296%	$5.9227	$5.92	$5.90	$5.90
Purchase #6	$113.82	4.769%	$119.2481	$119.25	$119.25	$119.20
Purchase #7	$226.92	10.561%	$250.885	$250.89	$250.90	$250.90
7 purchase totals =	$783.24		$860.8511	$860.86	$860.85	$860.70