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	$48.62	7.441%	$52.2378	$52.24	$52.25	$52.20
Purchase #2	$103.30	8.256%	$111.8284	$111.83	$111.85	$111.80
Purchase #3	$220.29	12.804%	$248.4959	$248.50	$248.50	$248.50
Purchase #4	$127.81	13.238%	$144.7295	$144.73	$144.75	$144.70
Purchase #5	$239.91	9.481%	$262.6559	$262.66	$262.65	$262.70
Purchase #6	$217.69	5.465%	$229.5868	$229.59	$229.60	$229.60
Purchase #7	$118.88	11.843%	$132.959	$132.96	$132.95	$133.00
7 purchase totals =	$1,076.50		$1,182.4933	$1,182.51	$1,182.55	$1,182.50