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	$205.28	4.214%	$213.9305	$213.93	$213.95	$213.90
Purchase #2	$250.38	6.377%	$266.3467	$266.35	$266.35	$266.30
Purchase #3	$10.65	9.117%	$11.621	$11.62	$11.60	$11.60
Purchase #4	$122.98	7.304%	$131.9625	$131.96	$131.95	$132.00
Purchase #5	$40.94	8.209%	$44.3008	$44.30	$44.30	$44.30
Purchase #6	$54.89	8.693%	$59.6616	$59.66	$59.65	$59.70
Purchase #7	$76.31	11.498%	$85.0841	$85.08	$85.10	$85.10
7 purchase totals =	$761.43		$812.9072	$812.90	$812.90	$812.90