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	$85.34	6.461%	$90.8538	$90.85	$90.85	$90.90
Purchase #2	$148.95	3.792%	$154.5982	$154.60	$154.60	$154.60
Purchase #3	$148.34	13.487%	$168.3466	$168.35	$168.35	$168.30
Purchase #4	$163.90	3.769%	$170.0774	$170.08	$170.10	$170.10
Purchase #5	$108.47	6.578%	$115.6052	$115.61	$115.60	$115.60
Purchase #6	$144.66	3.792%	$150.1455	$150.15	$150.15	$150.10
Purchase #7	$186.72	6.480%	$198.8195	$198.82	$198.80	$198.80
7 purchase totals =	$986.38		$1,048.4462	$1,048.46	$1,048.45	$1,048.40