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	$127.49	3.192%	$131.5595	$131.56	$131.55	$131.60
Purchase #2	$32.47	9.633%	$35.5978	$35.60	$35.60	$35.60
Purchase #3	$183.63	13.732%	$208.8461	$208.85	$208.85	$208.80
Purchase #4	$110.93	13.788%	$126.225	$126.23	$126.25	$126.20
Purchase #5	$225.78	10.804%	$250.1733	$250.17	$250.15	$250.20
Purchase #6	$100.92	8.322%	$109.3186	$109.32	$109.30	$109.30
Purchase #7	$127.44	3.680%	$132.1298	$132.13	$132.15	$132.10
7 purchase totals =	$908.66		$993.8501	$993.86	$993.85	$993.80