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	$200.83	7.855%	$216.6052	$216.61	$216.60	$216.60
Purchase #2	$130.60	10.558%	$144.3887	$144.39	$144.40	$144.40
Purchase #3	$222.90	10.787%	$246.9442	$246.94	$246.95	$246.90
Purchase #4	$118.75	12.213%	$133.2529	$133.25	$133.25	$133.30
Purchase #5	$137.53	5.791%	$145.4944	$145.49	$145.50	$145.50
Purchase #6	$115.84	6.495%	$123.3638	$123.36	$123.35	$123.40
Purchase #7	$116.44	4.302%	$121.4492	$121.45	$121.45	$121.40
7 purchase totals =	$1,042.89		$1,131.4984	$1,131.49	$1,131.50	$1,131.50