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	$152.29	12.554%	$171.4085	$171.41	$171.40	$171.40
Purchase #2	$246.26	6.379%	$261.9689	$261.97	$261.95	$262.00
Purchase #3	$123.55	12.632%	$139.1568	$139.16	$139.15	$139.20
Purchase #4	$128.99	8.274%	$139.6626	$139.66	$139.65	$139.70
Purchase #5	$26.54	5.527%	$28.0069	$28.01	$28.00	$28.00
Purchase #6	$179.44	6.178%	$190.5258	$190.53	$190.55	$190.50
Purchase #7	$141.76	9.138%	$154.714	$154.71	$154.70	$154.70
7 purchase totals =	$998.83		$1,085.4435	$1,085.45	$1,085.40	$1,085.50