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	$136.58	8.808%	$148.61	$148.61	$148.60	$148.60
Purchase #2	$83.25	3.210%	$85.9223	$85.92	$85.90	$85.90
Purchase #3	$176.65	3.324%	$182.5218	$182.52	$182.50	$182.50
Purchase #4	$88.34	3.523%	$91.4522	$91.45	$91.45	$91.50
Purchase #5	$127.58	4.243%	$132.9932	$132.99	$133.00	$133.00
Purchase #6	$177.38	3.217%	$183.0863	$183.09	$183.10	$183.10
Purchase #7	$229.72	10.477%	$253.7878	$253.79	$253.80	$253.80
7 purchase totals =	$1,019.50		$1,078.3736	$1,078.37	$1,078.35	$1,078.40