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	$114.37	11.105%	$127.0708	$127.07	$127.05	$127.10
Purchase #2	$130.89	11.590%	$146.0602	$146.06	$146.05	$146.10
Purchase #3	$236.45	12.211%	$265.3229	$265.32	$265.30	$265.30
Purchase #4	$15.98	4.855%	$16.7558	$16.76	$16.75	$16.80
Purchase #5	$15.86	7.408%	$17.0349	$17.03	$17.05	$17.00
Purchase #6	$59.50	10.159%	$65.5446	$65.54	$65.55	$65.50
Purchase #7	$152.43	5.538%	$160.8716	$160.87	$160.85	$160.90
7 purchase totals =	$725.48		$798.6608	$798.65	$798.60	$798.70