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	$87.70	7.273%	$94.0784	$94.08	$94.10	$94.10
Purchase #2	$7.40	7.218%	$7.9341	$7.93	$7.95	$7.90
Purchase #3	$250.43	11.503%	$279.237	$279.24	$279.25	$279.20
Purchase #4	$97.89	5.228%	$103.0077	$103.01	$103.00	$103.00
Purchase #5	$71.83	9.400%	$78.582	$78.58	$78.60	$78.60
Purchase #6	$197.78	13.854%	$225.1804	$225.18	$225.20	$225.20
Purchase #7	$122.35	4.339%	$127.6588	$127.66	$127.65	$127.70
7 purchase totals =	$835.38		$915.6784	$915.68	$915.75	$915.70