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	$164.89	5.787%	$174.4322	$174.43	$174.45	$174.40
Purchase #2	$143.75	8.581%	$156.0852	$156.09	$156.10	$156.10
Purchase #3	$118.65	10.529%	$131.1427	$131.14	$131.15	$131.10
Purchase #4	$174.32	11.205%	$193.8526	$193.85	$193.85	$193.90
Purchase #5	$172.61	8.108%	$186.6052	$186.61	$186.60	$186.60
Purchase #6	$21.89	9.603%	$23.9921	$23.99	$24.00	$24.00
Purchase #7	$123.45	10.577%	$136.5073	$136.51	$136.50	$136.50
7 purchase totals =	$919.56		$1,002.6173	$1,002.62	$1,002.65	$1,002.60