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	$13.65	6.240%	$14.5018	$14.50	$14.50	$14.50
Purchase #2	$41.98	4.555%	$43.8922	$43.89	$43.90	$43.90
Purchase #3	$77.74	7.515%	$83.5822	$83.58	$83.60	$83.60
Purchase #4	$108.70	5.349%	$114.5144	$114.51	$114.50	$114.50
Purchase #5	$85.71	5.586%	$90.4978	$90.50	$90.50	$90.50
Purchase #6	$224.49	6.218%	$238.4488	$238.45	$238.45	$238.40
Purchase #7	$146.44	7.202%	$156.9866	$156.99	$157.00	$157.00
7 purchase totals =	$698.71		$742.4238	$742.42	$742.45	$742.40