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	$73.25	5.196%	$77.0561	$77.06	$77.05	$77.10
Purchase #2	$53.33	10.602%	$58.984	$58.98	$59.00	$59.00
Purchase #3	$221.53	4.320%	$231.1001	$231.10	$231.10	$231.10
Purchase #4	$156.79	10.724%	$173.6042	$173.60	$173.60	$173.60
Purchase #5	$128.92	5.866%	$136.4824	$136.48	$136.50	$136.50
Purchase #6	$114.85	7.291%	$123.2237	$123.22	$123.20	$123.20
Purchase #7	$215.91	8.277%	$233.7809	$233.78	$233.80	$233.80
7 purchase totals =	$964.58		$1,034.2314	$1,034.22	$1,034.25	$1,034.30