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	$68.34	7.203%	$73.2625	$73.26	$73.25	$73.30
Purchase #2	$100.86	6.756%	$107.6741	$107.67	$107.65	$107.70
Purchase #3	$131.82	10.345%	$145.4568	$145.46	$145.45	$145.50
Purchase #4	$127.42	7.659%	$137.1791	$137.18	$137.20	$137.20
Purchase #5	$48.79	7.667%	$52.5307	$52.53	$52.55	$52.50
Purchase #6	$199.96	4.756%	$209.4701	$209.47	$209.45	$209.50
Purchase #7	$65.29	10.383%	$72.0691	$72.07	$72.05	$72.10
7 purchase totals =	$742.48		$797.6424	$797.64	$797.60	$797.80