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	$106.87	9.383%	$116.8976	$116.90	$116.90	$116.90
Purchase #2	$88.35	11.386%	$98.4095	$98.41	$98.40	$98.40
Purchase #3	$69.92	12.291%	$78.5139	$78.51	$78.50	$78.50
Purchase #4	$97.80	7.384%	$105.0216	$105.02	$105.00	$105.00
Purchase #5	$132.60	8.231%	$143.5143	$143.51	$143.50	$143.50
Purchase #6	$25.32	6.487%	$26.9625	$26.96	$26.95	$27.00
Purchase #7	$247.65	3.431%	$256.1469	$256.15	$256.15	$256.10
7 purchase totals =	$768.51		$825.4663	$825.46	$825.40	$825.40