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	$148.58	7.321%	$159.4575	$159.46	$159.45	$159.50
Purchase #2	$168.85	9.274%	$184.5091	$184.51	$184.50	$184.50
Purchase #3	$195.56	8.714%	$212.6011	$212.60	$212.60	$212.60
Purchase #4	$72.75	7.838%	$78.4521	$78.45	$78.45	$78.50
Purchase #5	$37.56	10.234%	$41.4039	$41.40	$41.40	$41.40
Purchase #6	$126.76	12.577%	$142.7026	$142.70	$142.70	$142.70
Purchase #7	$128.39	3.429%	$132.7925	$132.79	$132.80	$132.80
7 purchase totals =	$878.45		$951.9188	$951.91	$951.90	$952.00