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	$200.51	7.342%	$215.2314	$215.23	$215.25	$215.20
Purchase #2	$242.32	8.772%	$263.5763	$263.58	$263.60	$263.60
Purchase #3	$94.72	4.457%	$98.9417	$98.94	$98.95	$98.90
Purchase #4	$92.57	12.108%	$103.7784	$103.78	$103.80	$103.80
Purchase #5	$222.26	3.271%	$229.5301	$229.53	$229.55	$229.50
Purchase #6	$43.76	7.106%	$46.8696	$46.87	$46.85	$46.90
Purchase #7	$18.86	3.299%	$19.4822	$19.48	$19.50	$19.50
7 purchase totals =	$915.00		$977.4097	$977.41	$977.50	$977.40