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	$120.41	4.709%	$126.0801	$126.08	$126.10	$126.10
Purchase #2	$85.86	5.371%	$90.4715	$90.47	$90.45	$90.50
Purchase #3	$159.57	11.606%	$178.0897	$178.09	$178.10	$178.10
Purchase #4	$20.47	6.534%	$21.8075	$21.81	$21.80	$21.80
Purchase #5	$107.57	5.402%	$113.3809	$113.38	$113.40	$113.40
Purchase #6	$101.80	9.829%	$111.8059	$111.81	$111.80	$111.80
Purchase #7	$217.67	5.407%	$229.4394	$229.44	$229.45	$229.40
7 purchase totals =	$813.35		$871.0750	$871.08	$871.10	$871.10