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	$29.82	8.844%	$32.4573	$32.46	$32.45	$32.50
Purchase #2	$200.72	5.855%	$212.4722	$212.47	$212.45	$212.50
Purchase #3	$186.50	5.672%	$197.0783	$197.08	$197.10	$197.10
Purchase #4	$217.78	11.301%	$242.3913	$242.39	$242.40	$242.40
Purchase #5	$16.51	12.613%	$18.5924	$18.59	$18.60	$18.60
Purchase #6	$206.99	13.736%	$235.4221	$235.42	$235.40	$235.40
Purchase #7	$222.70	4.840%	$233.4787	$233.48	$233.50	$233.50
7 purchase totals =	$1,081.02		$1,171.8923	$1,171.89	$1,171.90	$1,172.00