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	$107.89	4.111%	$112.3254	$112.33	$112.35	$112.30
Purchase #2	$72.89	8.339%	$78.9683	$78.97	$78.95	$79.00
Purchase #3	$9.97	5.180%	$10.4864	$10.49	$10.50	$10.50
Purchase #4	$205.78	8.570%	$223.4153	$223.42	$223.40	$223.40
Purchase #5	$124.50	6.645%	$132.773	$132.77	$132.75	$132.80
Purchase #6	$245.39	10.867%	$272.0565	$272.06	$272.05	$272.10
Purchase #7	$74.99	11.286%	$83.4534	$83.45	$83.45	$83.50
7 purchase totals =	$841.41		$913.4783	$913.49	$913.45	$913.60