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	$245.75	4.504%	$256.8186	$256.82	$256.80	$256.80
Purchase #2	$76.73	7.439%	$82.4379	$82.44	$82.45	$82.40
Purchase #3	$44.50	13.238%	$50.3909	$50.39	$50.40	$50.40
Purchase #4	$63.51	13.683%	$72.2001	$72.20	$72.20	$72.20
Purchase #5	$246.39	8.333%	$266.9217	$266.92	$266.90	$266.90
Purchase #6	$119.88	10.664%	$132.664	$132.66	$132.65	$132.70
Purchase #7	$130.36	7.255%	$139.8176	$139.82	$139.80	$139.80
7 purchase totals =	$927.12		$1,001.2508	$1,001.25	$1,001.20	$1,001.20