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	$177.38	8.504%	$192.4644	$192.46	$192.45	$192.50
Purchase #2	$58.90	7.478%	$63.3045	$63.30	$63.30	$63.30
Purchase #3	$227.45	8.363%	$246.4716	$246.47	$246.45	$246.50
Purchase #4	$83.46	3.761%	$86.5989	$86.60	$86.60	$86.60
Purchase #5	$38.71	6.627%	$41.2753	$41.28	$41.30	$41.30
Purchase #6	$17.49	4.710%	$18.3138	$18.31	$18.30	$18.30
Purchase #7	$121.70	4.766%	$127.5002	$127.50	$127.50	$127.50
7 purchase totals =	$725.09		$775.9287	$775.92	$775.90	$776.00