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	$188.72	13.575%	$214.3387	$214.34	$214.35	$214.30
Purchase #2	$126.36	13.339%	$143.2152	$143.22	$143.20	$143.20
Purchase #3	$79.76	13.312%	$90.3777	$90.38	$90.40	$90.40
Purchase #4	$42.39	3.342%	$43.8067	$43.81	$43.80	$43.80
Purchase #5	$228.90	12.866%	$258.3503	$258.35	$258.35	$258.40
Purchase #6	$31.32	7.737%	$33.7432	$33.74	$33.75	$33.70
Purchase #7	$231.37	9.352%	$253.0077	$253.01	$253.00	$253.00
7 purchase totals =	$928.82		$1,036.8395	$1,036.85	$1,036.85	$1,036.80