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	$105.36	6.827%	$112.5529	$112.55	$112.55	$112.60
Purchase #2	$118.32	11.136%	$131.4961	$131.50	$131.50	$131.50
Purchase #3	$68.84	13.285%	$77.9854	$77.99	$78.00	$78.00
Purchase #4	$76.97	12.321%	$86.4535	$86.45	$86.45	$86.50
Purchase #5	$163.49	6.722%	$174.4798	$174.48	$174.50	$174.50
Purchase #6	$164.54	4.820%	$172.4708	$172.47	$172.45	$172.50
Purchase #7	$63.82	9.418%	$69.8306	$69.83	$69.85	$69.80
7 purchase totals =	$761.34		$825.2691	$825.27	$825.30	$825.40