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	$108.32	6.712%	$115.5904	$115.59	$115.60	$115.60
Purchase #2	$107.54	3.758%	$111.5814	$111.58	$111.60	$111.60
Purchase #3	$70.41	3.466%	$72.8504	$72.85	$72.85	$72.90
Purchase #4	$88.45	9.513%	$96.8642	$96.86	$96.85	$96.90
Purchase #5	$172.56	10.556%	$190.7754	$190.78	$190.80	$190.80
Purchase #6	$201.80	3.445%	$208.752	$208.75	$208.75	$208.80
Purchase #7	$213.39	13.677%	$242.5754	$242.58	$242.60	$242.60
7 purchase totals =	$962.47		$1,038.9892	$1,038.99	$1,039.05	$1,039.20