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	$5.52	4.458%	$5.7661	$5.77	$5.75	$5.80
Purchase #2	$16.43	13.640%	$18.6711	$18.67	$18.65	$18.70
Purchase #3	$113.60	8.357%	$123.0936	$123.09	$123.10	$123.10
Purchase #4	$172.44	10.581%	$190.6859	$190.69	$190.70	$190.70
Purchase #5	$142.89	5.233%	$150.3674	$150.37	$150.35	$150.40
Purchase #6	$247.48	3.483%	$256.0997	$256.10	$256.10	$256.10
Purchase #7	$241.51	11.239%	$268.6533	$268.65	$268.65	$268.70
7 purchase totals =	$939.87		$1,013.3371	$1,013.34	$1,013.30	$1,013.50