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	$185.81	10.269%	$204.8908	$204.89	$204.90	$204.90
Purchase #2	$212.79	10.531%	$235.1989	$235.20	$235.20	$235.20
Purchase #3	$103.48	10.342%	$114.1819	$114.18	$114.20	$114.20
Purchase #4	$113.59	8.751%	$123.5303	$123.53	$123.55	$123.50
Purchase #5	$177.60	7.375%	$190.698	$190.70	$190.70	$190.70
Purchase #6	$166.67	3.230%	$172.0534	$172.05	$172.05	$172.10
Purchase #7	$97.88	5.491%	$103.2546	$103.25	$103.25	$103.30
7 purchase totals =	$1,057.82		$1,143.8079	$1,143.80	$1,143.85	$1,143.90