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	$119.66	9.867%	$131.4669	$131.47	$131.45	$131.50
Purchase #2	$235.71	11.566%	$262.9722	$262.97	$262.95	$263.00
Purchase #3	$242.78	6.559%	$258.7039	$258.70	$258.70	$258.70
Purchase #4	$40.90	4.265%	$42.6444	$42.64	$42.65	$42.60
Purchase #5	$174.36	6.137%	$185.0605	$185.06	$185.05	$185.10
Purchase #6	$130.57	10.756%	$144.6141	$144.61	$144.60	$144.60
Purchase #7	$240.59	3.300%	$248.5295	$248.53	$248.55	$248.50
7 purchase totals =	$1,184.57		$1,273.9915	$1,273.98	$1,273.95	$1,274.00