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	$95.38	4.352%	$99.5309	$99.53	$99.55	$99.50
Purchase #2	$166.83	7.831%	$179.8945	$179.89	$179.90	$179.90
Purchase #3	$45.55	5.666%	$48.1309	$48.13	$48.15	$48.10
Purchase #4	$105.71	11.349%	$117.707	$117.71	$117.70	$117.70
Purchase #5	$214.59	4.380%	$223.989	$223.99	$224.00	$224.00
Purchase #6	$27.31	8.207%	$29.5513	$29.55	$29.55	$29.60
Purchase #7	$141.50	6.514%	$150.7173	$150.72	$150.70	$150.70
7 purchase totals =	$796.87		$849.5209	$849.52	$849.55	$849.50