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	$139.46	9.659%	$152.9304	$152.93	$152.95	$152.90
Purchase #2	$228.28	3.151%	$235.4731	$235.47	$235.45	$235.50
Purchase #3	$104.69	6.593%	$111.5922	$111.59	$111.60	$111.60
Purchase #4	$28.33	12.206%	$31.788	$31.79	$31.80	$31.80
Purchase #5	$17.59	5.445%	$18.5478	$18.55	$18.55	$18.50
Purchase #6	$57.53	12.105%	$64.494	$64.49	$64.50	$64.50
Purchase #7	$48.79	9.126%	$53.2426	$53.24	$53.25	$53.20
7 purchase totals =	$624.67		$668.0681	$668.06	$668.10	$668.00