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	$239.27	10.786%	$265.0777	$265.08	$265.10	$265.10
Purchase #2	$167.73	8.457%	$181.9149	$181.91	$181.90	$181.90
Purchase #3	$118.60	8.398%	$128.56	$128.56	$128.55	$128.60
Purchase #4	$159.55	8.272%	$172.748	$172.75	$172.75	$172.70
Purchase #5	$11.86	13.440%	$13.454	$13.45	$13.45	$13.50
Purchase #6	$132.70	4.618%	$138.8281	$138.83	$138.85	$138.80
Purchase #7	$179.64	9.114%	$196.0124	$196.01	$196.00	$196.00
7 purchase totals =	$1,009.35		$1,096.5951	$1,096.59	$1,096.60	$1,096.60