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	$241.81	13.300%	$273.9707	$273.97	$273.95	$274.00
Purchase #2	$172.95	13.801%	$196.8188	$196.82	$196.80	$196.80
Purchase #3	$17.90	13.455%	$20.3084	$20.31	$20.30	$20.30
Purchase #4	$26.89	7.861%	$29.0038	$29.00	$29.00	$29.00
Purchase #5	$63.51	3.373%	$65.6522	$65.65	$65.65	$65.70
Purchase #6	$81.47	11.371%	$90.734	$90.73	$90.75	$90.70
Purchase #7	$126.57	9.192%	$138.2043	$138.20	$138.20	$138.20
7 purchase totals =	$731.10		$814.6922	$814.68	$814.65	$814.70