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	$22.36	10.547%	$24.7183	$24.72	$24.70	$24.70
Purchase #2	$81.77	10.805%	$90.6052	$90.61	$90.60	$90.60
Purchase #3	$64.36	3.656%	$66.713	$66.71	$66.70	$66.70
Purchase #4	$116.89	8.177%	$126.4481	$126.45	$126.45	$126.40
Purchase #5	$208.50	11.539%	$232.5588	$232.56	$232.55	$232.60
Purchase #6	$117.80	4.775%	$123.425	$123.43	$123.45	$123.40
Purchase #7	$104.87	6.207%	$111.3793	$111.38	$111.40	$111.40
7 purchase totals =	$716.55		$775.8477	$775.86	$775.85	$775.80