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	$147.50	10.172%	$162.5037	$162.50	$162.50	$162.50
Purchase #2	$159.72	12.509%	$179.6994	$179.70	$179.70	$179.70
Purchase #3	$64.57	3.390%	$66.7589	$66.76	$66.75	$66.80
Purchase #4	$48.47	6.487%	$51.6142	$51.61	$51.60	$51.60
Purchase #5	$227.45	10.153%	$250.543	$250.54	$250.55	$250.50
Purchase #6	$178.96	3.441%	$185.118	$185.12	$185.10	$185.10
Purchase #7	$107.93	3.210%	$111.3946	$111.39	$111.40	$111.40
7 purchase totals =	$934.60		$1,007.6318	$1,007.62	$1,007.60	$1,007.60