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	$105.80	7.105%	$113.3171	$113.32	$113.30	$113.30
Purchase #2	$203.80	6.497%	$217.0409	$217.04	$217.05	$217.00
Purchase #3	$5.34	3.224%	$5.5122	$5.51	$5.50	$5.50
Purchase #4	$19.45	10.568%	$21.5055	$21.51	$21.50	$21.50
Purchase #5	$224.35	11.119%	$249.2955	$249.30	$249.30	$249.30
Purchase #6	$211.41	5.296%	$222.6063	$222.61	$222.60	$222.60
Purchase #7	$151.93	10.852%	$168.4174	$168.42	$168.40	$168.40
7 purchase totals =	$922.08		$997.6949	$997.71	$997.65	$997.60