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	$217.87	6.385%	$231.781	$231.78	$231.80	$231.80
Purchase #2	$34.78	7.509%	$37.3916	$37.39	$37.40	$37.40
Purchase #3	$44.54	6.463%	$47.4186	$47.42	$47.40	$47.40
Purchase #4	$73.99	5.552%	$78.0979	$78.10	$78.10	$78.10
Purchase #5	$9.55	13.570%	$10.8459	$10.85	$10.85	$10.80
Purchase #6	$184.91	7.366%	$198.5305	$198.53	$198.55	$198.50
Purchase #7	$131.74	4.207%	$137.2823	$137.28	$137.30	$137.30
7 purchase totals =	$697.38		$741.3478	$741.35	$741.40	$741.30