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	$221.54	10.865%	$245.6103	$245.61	$245.60	$245.60
Purchase #2	$142.77	8.768%	$155.2881	$155.29	$155.30	$155.30
Purchase #3	$63.78	4.768%	$66.821	$66.82	$66.80	$66.80
Purchase #4	$82.92	3.194%	$85.5685	$85.57	$85.55	$85.60
Purchase #5	$92.39	12.390%	$103.8371	$103.84	$103.85	$103.80
Purchase #6	$250.70	6.238%	$266.3387	$266.34	$266.35	$266.30
Purchase #7	$80.98	8.502%	$87.8649	$87.86	$87.85	$87.90
7 purchase totals =	$935.08		$1,011.3286	$1,011.33	$1,011.30	$1,011.30