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	$208.43	13.523%	$236.616	$236.62	$236.60	$236.60
Purchase #2	$172.88	13.475%	$196.1756	$196.18	$196.20	$196.20
Purchase #3	$219.65	6.766%	$234.5115	$234.51	$234.50	$234.50
Purchase #4	$160.49	5.537%	$169.3763	$169.38	$169.40	$169.40
Purchase #5	$82.58	4.666%	$86.4332	$86.43	$86.45	$86.40
Purchase #6	$163.96	7.781%	$176.7177	$176.72	$176.70	$176.70
Purchase #7	$89.57	10.329%	$98.8217	$98.82	$98.80	$98.80
7 purchase totals =	$1,097.56		$1,198.6520	$1,198.66	$1,198.65	$1,198.60