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	$126.85	6.331%	$134.8809	$134.88	$134.90	$134.90
Purchase #2	$121.87	13.542%	$138.3736	$138.37	$138.35	$138.40
Purchase #3	$47.72	7.431%	$51.2661	$51.27	$51.25	$51.30
Purchase #4	$86.70	3.225%	$89.4961	$89.50	$89.50	$89.50
Purchase #5	$29.54	10.720%	$32.7067	$32.71	$32.70	$32.70
Purchase #6	$169.93	5.690%	$179.599	$179.60	$179.60	$179.60
Purchase #7	$126.29	7.793%	$136.1318	$136.13	$136.15	$136.10
7 purchase totals =	$708.90		$762.4542	$762.46	$762.45	$762.50