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	$230.81	8.284%	$249.9303	$249.93	$249.95	$249.90
Purchase #2	$205.28	3.172%	$211.7915	$211.79	$211.80	$211.80
Purchase #3	$66.96	8.855%	$72.8893	$72.89	$72.90	$72.90
Purchase #4	$158.33	8.858%	$172.3549	$172.35	$172.35	$172.40
Purchase #5	$119.98	5.417%	$126.4793	$126.48	$126.50	$126.50
Purchase #6	$170.85	12.659%	$192.4779	$192.48	$192.50	$192.50
Purchase #7	$200.57	11.856%	$224.3496	$224.35	$224.35	$224.30
7 purchase totals =	$1,152.78		$1,250.2728	$1,250.27	$1,250.35	$1,250.30