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	$159.46	13.366%	$180.7734	$180.77	$180.75	$180.80
Purchase #2	$227.53	12.117%	$255.0998	$255.10	$255.10	$255.10
Purchase #3	$60.52	10.851%	$67.087	$67.09	$67.10	$67.10
Purchase #4	$160.36	8.724%	$174.3498	$174.35	$174.35	$174.30
Purchase #5	$91.26	8.648%	$99.1522	$99.15	$99.15	$99.20
Purchase #6	$133.60	7.406%	$143.4944	$143.49	$143.50	$143.50
Purchase #7	$139.29	3.528%	$144.2042	$144.20	$144.20	$144.20
7 purchase totals =	$972.02		$1,064.1608	$1,064.15	$1,064.15	$1,064.20