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	$68.59	7.633%	$73.8255	$73.83	$73.85	$73.80
Purchase #2	$226.59	4.675%	$237.1831	$237.18	$237.20	$237.20
Purchase #3	$11.45	6.561%	$12.2012	$12.20	$12.20	$12.20
Purchase #4	$230.64	10.564%	$255.0048	$255.00	$255.00	$255.00
Purchase #5	$47.86	9.609%	$52.4589	$52.46	$52.45	$52.50
Purchase #6	$241.85	13.667%	$274.9036	$274.90	$274.90	$274.90
Purchase #7	$90.79	3.372%	$93.8514	$93.85	$93.85	$93.90
7 purchase totals =	$917.77		$999.4285	$999.42	$999.45	$999.50