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	$37.83	9.189%	$41.3062	$41.31	$41.30	$41.30
Purchase #2	$226.60	10.437%	$250.2502	$250.25	$250.25	$250.30
Purchase #3	$178.97	6.389%	$190.4044	$190.40	$190.40	$190.40
Purchase #4	$126.86	4.577%	$132.6664	$132.67	$132.65	$132.70
Purchase #5	$132.52	4.804%	$138.8863	$138.89	$138.90	$138.90
Purchase #6	$187.72	12.855%	$211.8514	$211.85	$211.85	$211.90
Purchase #7	$158.99	5.205%	$167.2654	$167.27	$167.25	$167.30
7 purchase totals =	$1,049.49		$1,132.6303	$1,132.64	$1,132.60	$1,132.80