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	$141.73	13.312%	$160.5971	$160.60	$160.60	$160.60
Purchase #2	$87.75	13.850%	$99.9034	$99.90	$99.90	$99.90
Purchase #3	$125.42	12.804%	$141.4788	$141.48	$141.50	$141.50
Purchase #4	$128.32	11.456%	$143.0203	$143.02	$143.00	$143.00
Purchase #5	$191.66	12.413%	$215.4508	$215.45	$215.45	$215.50
Purchase #6	$144.48	8.597%	$156.9009	$156.90	$156.90	$156.90
Purchase #7	$113.58	8.808%	$123.5841	$123.58	$123.60	$123.60
7 purchase totals =	$932.94		$1,040.9354	$1,040.93	$1,040.95	$1,041.00