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	$108.29	6.623%	$115.462	$115.46	$115.45	$115.50
Purchase #2	$215.57	4.552%	$225.3827	$225.38	$225.40	$225.40
Purchase #3	$173.68	7.359%	$186.4611	$186.46	$186.45	$186.50
Purchase #4	$208.36	3.451%	$215.5505	$215.55	$215.55	$215.60
Purchase #5	$195.50	11.193%	$217.3823	$217.38	$217.40	$217.40
Purchase #6	$59.46	9.131%	$64.8893	$64.89	$64.90	$64.90
Purchase #7	$123.95	5.599%	$130.89	$130.89	$130.90	$130.90
7 purchase totals =	$1,084.81		$1,156.0179	$1,156.01	$1,156.05	$1,156.20