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	$237.60	4.824%	$249.0618	$249.06	$249.05	$249.10
Purchase #2	$159.74	6.342%	$169.8707	$169.87	$169.85	$169.90
Purchase #3	$249.57	3.320%	$257.8557	$257.86	$257.85	$257.90
Purchase #4	$108.42	7.655%	$116.7196	$116.72	$116.70	$116.70
Purchase #5	$66.90	13.477%	$75.9161	$75.92	$75.90	$75.90
Purchase #6	$81.42	11.683%	$90.9323	$90.93	$90.95	$90.90
Purchase #7	$82.31	5.178%	$86.572	$86.57	$86.55	$86.60
7 purchase totals =	$985.96		$1,046.9282	$1,046.93	$1,046.85	$1,047.00