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	$75.68	8.762%	$82.3111	$82.31	$82.30	$82.30
Purchase #2	$109.61	8.651%	$119.0924	$119.09	$119.10	$119.10
Purchase #3	$123.78	5.757%	$130.906	$130.91	$130.90	$130.90
Purchase #4	$60.39	10.484%	$66.7213	$66.72	$66.70	$66.70
Purchase #5	$199.67	7.183%	$214.0123	$214.01	$214.00	$214.00
Purchase #6	$177.81	5.658%	$187.8705	$187.87	$187.85	$187.90
Purchase #7	$31.89	5.382%	$33.6063	$33.61	$33.60	$33.60
7 purchase totals =	$778.83		$834.5199	$834.52	$834.45	$834.50