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	$128.31	11.836%	$143.4968	$143.50	$143.50	$143.50
Purchase #2	$172.56	3.231%	$178.1354	$178.14	$178.15	$178.10
Purchase #3	$146.25	4.624%	$153.0126	$153.01	$153.00	$153.00
Purchase #4	$98.29	4.557%	$102.7691	$102.77	$102.75	$102.80
Purchase #5	$216.80	13.171%	$245.3547	$245.35	$245.35	$245.40
Purchase #6	$205.88	12.735%	$232.0988	$232.10	$232.10	$232.10
Purchase #7	$39.39	5.636%	$41.61	$41.61	$41.60	$41.60
7 purchase totals =	$1,007.48		$1,096.4774	$1,096.48	$1,096.45	$1,096.50