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	$177.27	7.664%	$190.856	$190.86	$190.85	$190.90
Purchase #2	$97.82	8.292%	$105.9312	$105.93	$105.95	$105.90
Purchase #3	$31.83	10.223%	$35.084	$35.08	$35.10	$35.10
Purchase #4	$25.84	12.646%	$29.1077	$29.11	$29.10	$29.10
Purchase #5	$170.93	6.105%	$181.3653	$181.37	$181.35	$181.40
Purchase #6	$235.27	9.193%	$256.8984	$256.90	$256.90	$256.90
Purchase #7	$92.61	11.494%	$103.2546	$103.25	$103.25	$103.30
7 purchase totals =	$831.57		$902.4972	$902.50	$902.50	$902.60