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	$12.89	13.127%	$14.5821	$14.58	$14.60	$14.60
Purchase #2	$19.54	12.186%	$21.9211	$21.92	$21.90	$21.90
Purchase #3	$200.53	5.498%	$211.5551	$211.56	$211.55	$211.60
Purchase #4	$250.70	11.461%	$279.4327	$279.43	$279.45	$279.40
Purchase #5	$27.63	13.184%	$31.2727	$31.27	$31.25	$31.30
Purchase #6	$79.27	7.849%	$85.4919	$85.49	$85.50	$85.50
Purchase #7	$169.60	10.411%	$187.2571	$187.26	$187.25	$187.30
7 purchase totals =	$760.16		$831.5127	$831.51	$831.50	$831.60