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	9.552%	$219.6627	$219.66	$219.65	$219.70
Purchase #2	$8.58	6.226%	$9.1142	$9.11	$9.10	$9.10
Purchase #3	$89.74	11.416%	$99.9847	$99.98	$100.00	$100.00
Purchase #4	$208.60	11.701%	$233.0083	$233.01	$233.00	$233.00
Purchase #5	$68.53	5.159%	$72.0655	$72.07	$72.05	$72.10
Purchase #6	$108.36	13.805%	$123.3191	$123.32	$123.30	$123.30
Purchase #7	$247.75	3.527%	$256.4881	$256.49	$256.50	$256.50
7 purchase totals =	$932.07		$1,013.6426	$1,013.64	$1,013.60	$1,013.70