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	$161.39	4.447%	$168.567	$168.57	$168.55	$168.60
Purchase #2	$88.81	12.354%	$99.7816	$99.78	$99.80	$99.80
Purchase #3	$32.90	3.311%	$33.9893	$33.99	$34.00	$34.00
Purchase #4	$243.95	12.508%	$274.4633	$274.46	$274.45	$274.50
Purchase #5	$207.72	8.209%	$224.7717	$224.77	$224.75	$224.80
Purchase #6	$77.64	11.420%	$86.5065	$86.51	$86.50	$86.50
Purchase #7	$84.60	13.262%	$95.8197	$95.82	$95.80	$95.80
7 purchase totals =	$897.01		$983.8991	$983.90	$983.85	$984.00