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	$113.76	8.357%	$123.2669	$123.27	$123.25	$123.30
Purchase #2	$192.52	11.617%	$214.885	$214.89	$214.90	$214.90
Purchase #3	$192.40	12.185%	$215.8439	$215.84	$215.85	$215.80
Purchase #4	$148.36	8.493%	$160.9602	$160.96	$160.95	$161.00
Purchase #5	$173.75	13.116%	$196.5391	$196.54	$196.55	$196.50
Purchase #6	$241.47	3.569%	$250.0881	$250.09	$250.10	$250.10
Purchase #7	$225.48	3.765%	$233.9693	$233.97	$233.95	$234.00
7 purchase totals =	$1,287.74		$1,395.5525	$1,395.56	$1,395.55	$1,395.60