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	$220.50	11.154%	$245.0946	$245.09	$245.10	$245.10
Purchase #2	$180.52	10.415%	$199.3212	$199.32	$199.30	$199.30
Purchase #3	$72.28	5.214%	$76.0487	$76.05	$76.05	$76.00
Purchase #4	$190.32	4.270%	$198.4467	$198.45	$198.45	$198.40
Purchase #5	$59.68	12.719%	$67.2707	$67.27	$67.25	$67.30
Purchase #6	$46.45	3.793%	$48.2118	$48.21	$48.20	$48.20
Purchase #7	$227.28	10.372%	$250.8535	$250.85	$250.85	$250.90
7 purchase totals =	$997.03		$1,085.2472	$1,085.24	$1,085.20	$1,085.20