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	$194.96	10.695%	$215.811	$215.81	$215.80	$215.80
Purchase #2	$10.26	10.871%	$11.3754	$11.38	$11.40	$11.40
Purchase #3	$38.30	13.422%	$43.4406	$43.44	$43.45	$43.40
Purchase #4	$72.60	12.141%	$81.4144	$81.41	$81.40	$81.40
Purchase #5	$59.81	9.178%	$65.2994	$65.30	$65.30	$65.30
Purchase #6	$233.85	3.650%	$242.3855	$242.39	$242.40	$242.40
Purchase #7	$162.77	8.262%	$176.2181	$176.22	$176.20	$176.20
7 purchase totals =	$772.55		$835.9444	$835.95	$835.95	$835.90