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	$113.37	9.105%	$123.6923	$123.69	$123.70	$123.70
Purchase #2	$119.69	10.642%	$132.4274	$132.43	$132.45	$132.40
Purchase #3	$28.99	10.312%	$31.9794	$31.98	$32.00	$32.00
Purchase #4	$29.72	9.578%	$32.5666	$32.57	$32.55	$32.60
Purchase #5	$93.42	7.785%	$100.6927	$100.69	$100.70	$100.70
Purchase #6	$215.39	4.874%	$225.8881	$225.89	$225.90	$225.90
Purchase #7	$243.50	6.134%	$258.4363	$258.44	$258.45	$258.40
7 purchase totals =	$844.08		$905.6828	$905.69	$905.75	$905.70