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	$132.88	13.221%	$150.4481	$150.45	$150.45	$150.40
Purchase #2	$29.83	8.747%	$32.4392	$32.44	$32.45	$32.40
Purchase #3	$81.51	5.222%	$85.7665	$85.77	$85.75	$85.80
Purchase #4	$118.40	11.510%	$132.0278	$132.03	$132.05	$132.00
Purchase #5	$123.53	3.464%	$127.8091	$127.81	$127.80	$127.80
Purchase #6	$92.94	11.794%	$103.9013	$103.90	$103.90	$103.90
Purchase #7	$212.27	3.848%	$220.4381	$220.44	$220.45	$220.40
7 purchase totals =	$791.36		$852.8301	$852.84	$852.85	$852.70