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	$59.69	8.249%	$64.6138	$64.61	$64.60	$64.60
Purchase #2	$204.44	6.278%	$217.2747	$217.27	$217.25	$217.30
Purchase #3	$93.72	12.796%	$105.7124	$105.71	$105.70	$105.70
Purchase #4	$34.64	5.225%	$36.4499	$36.45	$36.45	$36.40
Purchase #5	$189.49	4.718%	$198.4301	$198.43	$198.45	$198.40
Purchase #6	$173.50	7.521%	$186.5489	$186.55	$186.55	$186.50
Purchase #7	$234.28	9.478%	$256.4851	$256.49	$256.50	$256.50
7 purchase totals =	$989.76		$1,065.5149	$1,065.51	$1,065.50	$1,065.40