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	$205.75	9.785%	$225.8826	$225.88	$225.90	$225.90
Purchase #2	$214.72	3.610%	$222.4714	$222.47	$222.45	$222.50
Purchase #3	$186.33	6.459%	$198.3651	$198.37	$198.35	$198.40
Purchase #4	$115.70	4.678%	$121.1124	$121.11	$121.10	$121.10
Purchase #5	$126.60	12.161%	$141.9958	$142.00	$142.00	$142.00
Purchase #6	$197.51	12.626%	$222.4476	$222.45	$222.45	$222.40
Purchase #7	$113.37	9.207%	$123.808	$123.81	$123.80	$123.80
7 purchase totals =	$1,159.98		$1,256.0829	$1,256.09	$1,256.05	$1,256.10