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	$143.48	4.797%	$150.3627	$150.36	$150.35	$150.40
Purchase #2	$153.88	9.501%	$168.5001	$168.50	$168.50	$168.50
Purchase #3	$200.84	5.587%	$212.0609	$212.06	$212.05	$212.10
Purchase #4	$28.89	10.602%	$31.9529	$31.95	$31.95	$32.00
Purchase #5	$82.97	7.828%	$89.4649	$89.46	$89.45	$89.50
Purchase #6	$7.36	5.758%	$7.7838	$7.78	$7.80	$7.80
Purchase #7	$13.82	13.115%	$15.6325	$15.63	$15.65	$15.60
7 purchase totals =	$631.24		$675.7578	$675.74	$675.75	$675.90