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	$115.47	3.282%	$119.2597	$119.26	$119.25	$119.30
Purchase #2	$242.96	5.131%	$255.4263	$255.43	$255.45	$255.40
Purchase #3	$90.64	9.327%	$99.094	$99.09	$99.10	$99.10
Purchase #4	$8.72	13.393%	$9.8879	$9.89	$9.90	$9.90
Purchase #5	$83.32	9.119%	$90.918	$90.92	$90.90	$90.90
Purchase #6	$184.60	13.722%	$209.9308	$209.93	$209.95	$209.90
Purchase #7	$231.49	3.534%	$239.6709	$239.67	$239.65	$239.70
7 purchase totals =	$957.20		$1,024.1876	$1,024.19	$1,024.20	$1,024.20