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	$192.70	11.757%	$215.3557	$215.36	$215.35	$215.40
Purchase #2	$215.60	12.624%	$242.8173	$242.82	$242.80	$242.80
Purchase #3	$33.89	10.494%	$37.4464	$37.45	$37.45	$37.40
Purchase #4	$250.81	12.679%	$282.6102	$282.61	$282.60	$282.60
Purchase #5	$143.30	8.118%	$154.9331	$154.93	$154.95	$154.90
Purchase #6	$139.40	3.337%	$144.0518	$144.05	$144.05	$144.10
Purchase #7	$124.48	11.656%	$138.9894	$138.99	$139.00	$139.00
7 purchase totals =	$1,100.18		$1,216.2039	$1,216.21	$1,216.20	$1,216.20