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	$114.92	10.544%	$127.0372	$127.04	$127.05	$127.00
Purchase #2	$63.56	11.131%	$70.6349	$70.63	$70.65	$70.60
Purchase #3	$32.32	10.843%	$35.8245	$35.82	$35.80	$35.80
Purchase #4	$145.41	5.128%	$152.8666	$152.87	$152.85	$152.90
Purchase #5	$109.64	12.872%	$123.7529	$123.75	$123.75	$123.80
Purchase #6	$150.80	5.180%	$158.6114	$158.61	$158.60	$158.60
Purchase #7	$146.42	7.602%	$157.5508	$157.55	$157.55	$157.60
7 purchase totals =	$763.07		$826.2783	$826.27	$826.25	$826.30