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	$60.49	5.262%	$63.673	$63.67	$63.65	$63.70
Purchase #2	$133.96	7.412%	$143.8891	$143.89	$143.90	$143.90
Purchase #3	$63.57	5.118%	$66.8235	$66.82	$66.80	$66.80
Purchase #4	$219.81	9.817%	$241.3887	$241.39	$241.40	$241.40
Purchase #5	$87.33	8.221%	$94.5094	$94.51	$94.50	$94.50
Purchase #6	$200.60	7.612%	$215.8697	$215.87	$215.85	$215.90
Purchase #7	$250.59	3.415%	$259.1476	$259.15	$259.15	$259.10
7 purchase totals =	$1,016.35		$1,085.3010	$1,085.30	$1,085.25	$1,085.30