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	$66.76	8.773%	$72.6169	$72.62	$72.60	$72.60
Purchase #2	$34.85	5.609%	$36.8047	$36.80	$36.80	$36.80
Purchase #3	$58.47	9.408%	$63.9709	$63.97	$63.95	$64.00
Purchase #4	$137.93	9.639%	$151.2251	$151.23	$151.25	$151.20
Purchase #5	$95.36	4.802%	$99.9392	$99.94	$99.95	$99.90
Purchase #6	$247.78	10.131%	$272.8826	$272.88	$272.90	$272.90
Purchase #7	$238.61	7.664%	$256.8971	$256.90	$256.90	$256.90
7 purchase totals =	$879.76		$954.3365	$954.34	$954.35	$954.30