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	$43.65	4.518%	$45.6221	$45.62	$45.60	$45.60
Purchase #2	$166.25	11.792%	$185.8542	$185.85	$185.85	$185.90
Purchase #3	$148.82	3.623%	$154.2117	$154.21	$154.20	$154.20
Purchase #4	$81.49	12.239%	$91.4636	$91.46	$91.45	$91.50
Purchase #5	$176.84	5.226%	$186.0817	$186.08	$186.10	$186.10
Purchase #6	$141.86	13.210%	$160.5997	$160.60	$160.60	$160.60
Purchase #7	$72.82	5.259%	$76.6496	$76.65	$76.65	$76.60
7 purchase totals =	$831.73		$900.4826	$900.47	$900.45	$900.50