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	$211.66	10.770%	$234.4558	$234.46	$234.45	$234.50
Purchase #2	$44.35	3.585%	$45.9399	$45.94	$45.95	$45.90
Purchase #3	$67.86	12.596%	$76.4076	$76.41	$76.40	$76.40
Purchase #4	$191.67	12.629%	$215.876	$215.88	$215.90	$215.90
Purchase #5	$192.76	3.127%	$198.7876	$198.79	$198.80	$198.80
Purchase #6	$50.78	13.181%	$57.4733	$57.47	$57.45	$57.50
Purchase #7	$236.34	4.268%	$246.427	$246.43	$246.45	$246.40
7 purchase totals =	$995.42		$1,075.3672	$1,075.38	$1,075.40	$1,075.40