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	$162.39	10.597%	$179.5985	$179.60	$179.60	$179.60
Purchase #2	$164.39	11.595%	$183.451	$183.45	$183.45	$183.50
Purchase #3	$94.59	9.277%	$103.3651	$103.37	$103.35	$103.40
Purchase #4	$231.83	10.469%	$256.1003	$256.10	$256.10	$256.10
Purchase #5	$128.32	12.107%	$143.8557	$143.86	$143.85	$143.90
Purchase #6	$80.27	11.108%	$89.1864	$89.19	$89.20	$89.20
Purchase #7	$16.57	5.542%	$17.4883	$17.49	$17.50	$17.50
7 purchase totals =	$878.36		$973.0453	$973.06	$973.05	$973.20