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	$152.70	10.510%	$168.7488	$168.75	$168.75	$168.70
Purchase #2	$132.53	8.291%	$143.5181	$143.52	$143.50	$143.50
Purchase #3	$117.92	4.732%	$123.5	$123.50	$123.50	$123.50
Purchase #4	$61.94	8.746%	$67.3573	$67.36	$67.35	$67.40
Purchase #5	$197.59	12.471%	$222.2314	$222.23	$222.25	$222.20
Purchase #6	$128.58	12.327%	$144.4301	$144.43	$144.45	$144.40
Purchase #7	$212.39	10.792%	$235.3111	$235.31	$235.30	$235.30
7 purchase totals =	$1,003.65		$1,105.0968	$1,105.10	$1,105.10	$1,105.00