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	$70.73	10.208%	$77.9501	$77.95	$77.95	$78.00
Purchase #2	$117.57	13.469%	$133.4055	$133.41	$133.40	$133.40
Purchase #3	$188.37	6.840%	$201.2545	$201.25	$201.25	$201.30
Purchase #4	$216.93	5.475%	$228.8069	$228.81	$228.80	$228.80
Purchase #5	$130.73	6.336%	$139.0131	$139.01	$139.00	$139.00
Purchase #6	$81.82	4.636%	$85.6132	$85.61	$85.60	$85.60
Purchase #7	$136.94	9.863%	$150.4464	$150.45	$150.45	$150.40
7 purchase totals =	$943.09		$1,016.4897	$1,016.49	$1,016.45	$1,016.50