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	$232.78	4.416%	$243.0596	$243.06	$243.05	$243.10
Purchase #2	$136.40	5.465%	$143.8543	$143.85	$143.85	$143.90
Purchase #3	$77.37	4.131%	$80.5662	$80.57	$80.55	$80.60
Purchase #4	$171.52	10.825%	$190.087	$190.09	$190.10	$190.10
Purchase #5	$157.83	9.197%	$172.3456	$172.35	$172.35	$172.30
Purchase #6	$31.84	7.554%	$34.2452	$34.25	$34.25	$34.20
Purchase #7	$249.89	12.373%	$280.8089	$280.81	$280.80	$280.80
7 purchase totals =	$1,057.63		$1,144.9668	$1,144.98	$1,144.95	$1,145.00