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	$197.49	8.177%	$213.6388	$213.64	$213.65	$213.60
Purchase #2	$34.33	4.622%	$35.9167	$35.92	$35.90	$35.90
Purchase #3	$204.27	13.244%	$231.3235	$231.32	$231.30	$231.30
Purchase #4	$60.56	11.531%	$67.5432	$67.54	$67.55	$67.50
Purchase #5	$102.33	9.626%	$112.1803	$112.18	$112.20	$112.20
Purchase #6	$32.51	6.229%	$34.535	$34.54	$34.55	$34.50
Purchase #7	$87.71	5.300%	$92.3586	$92.36	$92.35	$92.40
7 purchase totals =	$719.20		$787.4961	$787.50	$787.50	$787.40