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	$30.60	10.553%	$33.8292	$33.83	$33.85	$33.80
Purchase #2	$31.27	8.380%	$33.8904	$33.89	$33.90	$33.90
Purchase #3	$107.58	9.581%	$117.8872	$117.89	$117.90	$117.90
Purchase #4	$148.82	6.755%	$158.8728	$158.87	$158.85	$158.90
Purchase #5	$103.48	3.459%	$107.0594	$107.06	$107.05	$107.10
Purchase #6	$79.77	3.262%	$82.3721	$82.37	$82.35	$82.40
Purchase #7	$125.52	13.198%	$142.0861	$142.09	$142.10	$142.10
7 purchase totals =	$627.04		$675.9972	$676.00	$676.00	$676.10