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	$113.59	5.177%	$119.4706	$119.47	$119.45	$119.50
Purchase #2	$120.81	9.116%	$131.823	$131.82	$131.80	$131.80
Purchase #3	$234.51	8.274%	$253.9134	$253.91	$253.90	$253.90
Purchase #4	$249.42	10.187%	$274.8284	$274.83	$274.85	$274.80
Purchase #5	$102.77	9.322%	$112.3502	$112.35	$112.35	$112.40
Purchase #6	$132.46	8.321%	$143.482	$143.48	$143.50	$143.50
Purchase #7	$34.72	13.490%	$39.4037	$39.40	$39.40	$39.40
7 purchase totals =	$988.28		$1,075.2713	$1,075.26	$1,075.25	$1,075.30