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	$56.26	6.386%	$59.8528	$59.85	$59.85	$59.90
Purchase #2	$84.58	11.102%	$93.9701	$93.97	$93.95	$94.00
Purchase #3	$41.95	8.726%	$45.6106	$45.61	$45.60	$45.60
Purchase #4	$164.79	11.347%	$183.4887	$183.49	$183.50	$183.50
Purchase #5	$167.29	5.370%	$176.2735	$176.27	$176.25	$176.30
Purchase #6	$90.60	4.250%	$94.4505	$94.45	$94.45	$94.50
Purchase #7	$215.96	6.343%	$229.6583	$229.66	$229.65	$229.70
7 purchase totals =	$821.43		$883.3045	$883.30	$883.25	$883.50