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	$38.60	13.363%	$43.7581	$43.76	$43.75	$43.80
Purchase #2	$131.34	8.123%	$142.0087	$142.01	$142.00	$142.00
Purchase #3	$226.54	8.856%	$246.6024	$246.60	$246.60	$246.60
Purchase #4	$187.71	13.518%	$213.0846	$213.08	$213.10	$213.10
Purchase #5	$231.71	8.684%	$251.8317	$251.83	$251.85	$251.80
Purchase #6	$97.62	13.789%	$111.0808	$111.08	$111.10	$111.10
Purchase #7	$56.41	4.635%	$59.0246	$59.02	$59.00	$59.00
7 purchase totals =	$969.93		$1,067.3909	$1,067.38	$1,067.40	$1,067.40