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	$10.44	7.723%	$11.2463	$11.25	$11.25	$11.20
Purchase #2	$148.47	6.837%	$158.6209	$158.62	$158.60	$158.60
Purchase #3	$210.27	13.431%	$238.5114	$238.51	$238.50	$238.50
Purchase #4	$55.44	8.247%	$60.0121	$60.01	$60.00	$60.00
Purchase #5	$168.63	4.303%	$175.8861	$175.89	$175.90	$175.90
Purchase #6	$117.46	13.669%	$133.5156	$133.52	$133.50	$133.50
Purchase #7	$76.77	7.545%	$82.5623	$82.56	$82.55	$82.60
7 purchase totals =	$787.48		$860.3547	$860.36	$860.30	$860.30