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	$198.45	9.595%	$217.4913	$217.49	$217.50	$217.50
Purchase #2	$137.80	4.112%	$143.4663	$143.47	$143.45	$143.50
Purchase #3	$57.90	13.810%	$65.896	$65.90	$65.90	$65.90
Purchase #4	$182.27	12.409%	$204.8879	$204.89	$204.90	$204.90
Purchase #5	$147.91	8.756%	$160.861	$160.86	$160.85	$160.90
Purchase #6	$150.53	9.844%	$165.3482	$165.35	$165.35	$165.30
Purchase #7	$112.27	6.680%	$119.7696	$119.77	$119.75	$119.80
7 purchase totals =	$987.13		$1,077.7203	$1,077.73	$1,077.70	$1,077.80