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	$195.99	10.234%	$216.0476	$216.05	$216.05	$216.00
Purchase #2	$51.80	4.319%	$54.0372	$54.04	$54.05	$54.00
Purchase #3	$41.47	3.380%	$42.8717	$42.87	$42.85	$42.90
Purchase #4	$237.46	12.389%	$266.8789	$266.88	$266.90	$266.90
Purchase #5	$234.59	3.778%	$243.4528	$243.45	$243.45	$243.50
Purchase #6	$20.93	3.157%	$21.5908	$21.59	$21.60	$21.60
Purchase #7	$137.33	12.340%	$154.2765	$154.28	$154.30	$154.30
7 purchase totals =	$919.57		$999.1555	$999.16	$999.20	$999.20