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	$114.53	3.419%	$118.4458	$118.45	$118.45	$118.40
Purchase #2	$212.86	13.503%	$241.6025	$241.60	$241.60	$241.60
Purchase #3	$132.90	7.290%	$142.5884	$142.59	$142.60	$142.60
Purchase #4	$242.62	12.262%	$272.3701	$272.37	$272.35	$272.40
Purchase #5	$38.83	12.796%	$43.7987	$43.80	$43.80	$43.80
Purchase #6	$17.50	13.474%	$19.858	$19.86	$19.85	$19.90
Purchase #7	$95.65	8.652%	$103.9256	$103.93	$103.95	$103.90
7 purchase totals =	$854.89		$942.5891	$942.60	$942.60	$942.60