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	$181.48	10.186%	$199.9656	$199.97	$199.95	$200.00
Purchase #2	$59.78	13.403%	$67.7923	$67.79	$67.80	$67.80
Purchase #3	$65.69	6.648%	$70.0571	$70.06	$70.05	$70.10
Purchase #4	$51.37	9.518%	$56.2594	$56.26	$56.25	$56.30
Purchase #5	$68.49	4.525%	$71.5892	$71.59	$71.60	$71.60
Purchase #6	$154.84	6.152%	$164.3658	$164.37	$164.35	$164.40
Purchase #7	$99.96	5.754%	$105.7117	$105.71	$105.70	$105.70
7 purchase totals =	$681.61		$735.7411	$735.75	$735.70	$735.90