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	$45.95	6.259%	$48.826	$48.83	$48.85	$48.80
Purchase #2	$116.38	13.785%	$132.423	$132.42	$132.40	$132.40
Purchase #3	$137.46	11.204%	$152.861	$152.86	$152.85	$152.90
Purchase #4	$214.29	9.316%	$234.2533	$234.25	$234.25	$234.30
Purchase #5	$72.25	8.649%	$78.4989	$78.50	$78.50	$78.50
Purchase #6	$49.91	13.596%	$56.6958	$56.70	$56.70	$56.70
Purchase #7	$127.86	11.797%	$142.9436	$142.94	$142.95	$142.90
7 purchase totals =	$764.10		$846.5016	$846.50	$846.50	$846.50