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	$233.96	7.506%	$251.521	$251.52	$251.50	$251.50
Purchase #2	$215.57	8.407%	$233.693	$233.69	$233.70	$233.70
Purchase #3	$78.59	6.719%	$83.8705	$83.87	$83.85	$83.90
Purchase #4	$100.60	6.856%	$107.4971	$107.50	$107.50	$107.50
Purchase #5	$116.82	5.635%	$123.4028	$123.40	$123.40	$123.40
Purchase #6	$166.83	6.855%	$178.2662	$178.27	$178.25	$178.30
Purchase #7	$63.37	13.661%	$72.027	$72.03	$72.05	$72.00
7 purchase totals =	$975.74		$1,050.2776	$1,050.28	$1,050.25	$1,050.30