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	$205.63	13.754%	$233.9124	$233.91	$233.90	$233.90
Purchase #2	$87.94	3.288%	$90.8315	$90.83	$90.85	$90.80
Purchase #3	$74.44	5.390%	$78.4523	$78.45	$78.45	$78.50
Purchase #4	$138.93	7.821%	$149.7957	$149.80	$149.80	$149.80
Purchase #5	$25.39	7.364%	$27.2597	$27.26	$27.25	$27.30
Purchase #6	$96.90	4.204%	$100.9737	$100.97	$100.95	$101.00
Purchase #7	$54.40	11.682%	$60.755	$60.76	$60.75	$60.80
7 purchase totals =	$683.63		$741.9803	$741.98	$741.95	$742.10