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	$242.42	5.425%	$255.5713	$255.57	$255.55	$255.60
Purchase #2	$45.26	6.442%	$48.1756	$48.18	$48.20	$48.20
Purchase #3	$200.40	11.228%	$222.9009	$222.90	$222.90	$222.90
Purchase #4	$219.31	5.583%	$231.5541	$231.55	$231.55	$231.60
Purchase #5	$214.90	12.858%	$242.5318	$242.53	$242.55	$242.50
Purchase #6	$202.87	7.201%	$217.4787	$217.48	$217.50	$217.50
Purchase #7	$96.52	9.509%	$105.6981	$105.70	$105.70	$105.70
7 purchase totals =	$1,221.68		$1,323.9105	$1,323.91	$1,323.95	$1,324.00