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	$10.51	4.793%	$11.0137	$11.01	$11.00	$11.00
Purchase #2	$40.85	11.215%	$45.4313	$45.43	$45.45	$45.40
Purchase #3	$34.63	6.460%	$36.8671	$36.87	$36.85	$36.90
Purchase #4	$176.71	5.589%	$186.5863	$186.59	$186.60	$186.60
Purchase #5	$16.51	6.671%	$17.6114	$17.61	$17.60	$17.60
Purchase #6	$41.61	9.489%	$45.5584	$45.56	$45.55	$45.60
Purchase #7	$122.78	11.344%	$136.7082	$136.71	$136.70	$136.70
7 purchase totals =	$443.60		$479.7764	$479.78	$479.75	$479.80