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	$18.61	9.859%	$20.4448	$20.44	$20.45	$20.40
Purchase #2	$58.82	5.581%	$62.1027	$62.10	$62.10	$62.10
Purchase #3	$41.46	8.273%	$44.89	$44.89	$44.90	$44.90
Purchase #4	$90.64	3.242%	$93.5785	$93.58	$93.60	$93.60
Purchase #5	$85.25	8.318%	$92.3411	$92.34	$92.35	$92.30
Purchase #6	$174.59	3.313%	$180.3742	$180.37	$180.35	$180.40
Purchase #7	$210.57	13.396%	$238.778	$238.78	$238.80	$238.80
7 purchase totals =	$679.94		$732.5093	$732.50	$732.55	$732.50