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	$111.78	13.798%	$127.2034	$127.20	$127.20	$127.20
Purchase #2	$165.32	4.863%	$173.3595	$173.36	$173.35	$173.40
Purchase #3	$32.90	9.327%	$35.9686	$35.97	$35.95	$36.00
Purchase #4	$148.82	5.105%	$156.4173	$156.42	$156.40	$156.40
Purchase #5	$97.52	3.181%	$100.6221	$100.62	$100.60	$100.60
Purchase #6	$179.99	6.542%	$191.7649	$191.76	$191.75	$191.80
Purchase #7	$167.85	3.799%	$174.2266	$174.23	$174.25	$174.20
7 purchase totals =	$904.18		$959.5624	$959.56	$959.50	$959.60