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	$62.99	7.104%	$67.4648	$67.46	$67.45	$67.50
Purchase #2	$204.31	8.863%	$222.418	$222.42	$222.40	$222.40
Purchase #3	$198.58	8.396%	$215.2528	$215.25	$215.25	$215.30
Purchase #4	$37.26	9.118%	$40.6574	$40.66	$40.65	$40.70
Purchase #5	$108.76	3.443%	$112.5046	$112.50	$112.50	$112.50
Purchase #6	$206.94	10.818%	$229.3268	$229.33	$229.35	$229.30
Purchase #7	$12.50	10.857%	$13.8571	$13.86	$13.85	$13.90
7 purchase totals =	$831.34		$901.4815	$901.48	$901.45	$901.60