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	$114.48	11.480%	$127.6223	$127.62	$127.60	$127.60
Purchase #2	$47.62	9.202%	$52.002	$52.00	$52.00	$52.00
Purchase #3	$110.40	12.188%	$123.8556	$123.86	$123.85	$123.90
Purchase #4	$17.40	10.330%	$19.1974	$19.20	$19.20	$19.20
Purchase #5	$63.76	8.423%	$69.1305	$69.13	$69.15	$69.10
Purchase #6	$59.54	11.795%	$66.5627	$66.56	$66.55	$66.60
Purchase #7	$59.52	10.770%	$65.9303	$65.93	$65.95	$65.90
7 purchase totals =	$472.72		$524.3008	$524.30	$524.30	$524.30