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	$57.80	7.273%	$62.0038	$62.00	$62.00	$62.00
Purchase #2	$154.81	5.693%	$163.6233	$163.62	$163.60	$163.60
Purchase #3	$174.30	4.779%	$182.6298	$182.63	$182.65	$182.60
Purchase #4	$29.29	6.780%	$31.2759	$31.28	$31.30	$31.30
Purchase #5	$86.82	3.833%	$90.1478	$90.15	$90.15	$90.10
Purchase #6	$105.56	12.374%	$118.622	$118.62	$118.60	$118.60
Purchase #7	$13.40	3.603%	$13.8828	$13.88	$13.90	$13.90
7 purchase totals =	$621.98		$662.1854	$662.18	$662.20	$662.10