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	$221.32	6.558%	$235.8342	$235.83	$235.85	$235.80
Purchase #2	$120.58	4.126%	$125.5551	$125.56	$125.55	$125.60
Purchase #3	$54.38	9.287%	$59.4303	$59.43	$59.45	$59.40
Purchase #4	$72.51	10.831%	$80.3636	$80.36	$80.35	$80.40
Purchase #5	$246.25	10.839%	$272.941	$272.94	$272.95	$272.90
Purchase #6	$59.64	10.730%	$66.0394	$66.04	$66.05	$66.00
Purchase #7	$26.41	5.553%	$27.8765	$27.88	$27.90	$27.90
7 purchase totals =	$801.09		$868.0401	$868.04	$868.10	$868.00