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	$120.82	11.113%	$134.2467	$134.25	$134.25	$134.20
Purchase #2	$132.60	6.528%	$141.2561	$141.26	$141.25	$141.30
Purchase #3	$13.65	4.462%	$14.2591	$14.26	$14.25	$14.30
Purchase #4	$160.72	7.124%	$172.1697	$172.17	$172.15	$172.20
Purchase #5	$75.82	12.443%	$85.2543	$85.25	$85.25	$85.30
Purchase #6	$131.48	8.276%	$142.3613	$142.36	$142.35	$142.40
Purchase #7	$143.47	13.618%	$163.0077	$163.01	$163.00	$163.00
7 purchase totals =	$778.56		$852.5549	$852.56	$852.50	$852.70