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	$126.71	13.874%	$144.2897	$144.29	$144.30	$144.30
Purchase #2	$235.59	11.771%	$263.3213	$263.32	$263.30	$263.30
Purchase #3	$235.43	8.513%	$255.4722	$255.47	$255.45	$255.50
Purchase #4	$108.98	4.778%	$114.1871	$114.19	$114.20	$114.20
Purchase #5	$177.25	12.452%	$199.3212	$199.32	$199.30	$199.30
Purchase #6	$47.69	4.605%	$49.8861	$49.89	$49.90	$49.90
Purchase #7	$50.60	12.373%	$56.8607	$56.86	$56.85	$56.90
7 purchase totals =	$982.25		$1,083.3383	$1,083.34	$1,083.30	$1,083.40