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	$197.41	11.683%	$220.4734	$220.47	$220.45	$220.50
Purchase #2	$43.71	5.273%	$46.0148	$46.01	$46.00	$46.00
Purchase #3	$169.27	9.825%	$185.9008	$185.90	$185.90	$185.90
Purchase #4	$95.81	3.103%	$98.783	$98.78	$98.80	$98.80
Purchase #5	$172.47	8.651%	$187.3904	$187.39	$187.40	$187.40
Purchase #6	$142.70	5.335%	$150.313	$150.31	$150.30	$150.30
Purchase #7	$92.26	11.213%	$102.6051	$102.61	$102.60	$102.60
7 purchase totals =	$913.63		$991.4805	$991.47	$991.45	$991.50