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	$96.99	9.118%	$105.8335	$105.83	$105.85	$105.80
Purchase #2	$82.80	8.334%	$89.7006	$89.70	$89.70	$89.70
Purchase #3	$27.93	11.155%	$31.0456	$31.05	$31.05	$31.00
Purchase #4	$136.75	3.517%	$141.5595	$141.56	$141.55	$141.60
Purchase #5	$46.73	3.688%	$48.4534	$48.45	$48.45	$48.50
Purchase #6	$133.71	6.206%	$142.008	$142.01	$142.00	$142.00
Purchase #7	$64.87	11.696%	$72.4572	$72.46	$72.45	$72.50
7 purchase totals =	$589.78		$631.0578	$631.06	$631.05	$631.10