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	$10.40	10.688%	$11.5116	$11.51	$11.50	$11.50
Purchase #2	$98.35	11.714%	$109.8707	$109.87	$109.85	$109.90
Purchase #3	$127.75	8.779%	$138.9652	$138.97	$138.95	$139.00
Purchase #4	$158.59	8.342%	$171.8196	$171.82	$171.80	$171.80
Purchase #5	$66.85	8.495%	$72.5289	$72.53	$72.55	$72.50
Purchase #6	$245.61	12.164%	$275.486	$275.49	$275.50	$275.50
Purchase #7	$173.91	7.456%	$186.8767	$186.88	$186.90	$186.90
7 purchase totals =	$881.46		$967.0587	$967.07	$967.05	$967.10