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	$36.33	11.641%	$40.5592	$40.56	$40.55	$40.60
Purchase #2	$35.59	5.321%	$37.4837	$37.48	$37.50	$37.50
Purchase #3	$177.43	4.413%	$185.26	$185.26	$185.25	$185.30
Purchase #4	$231.47	10.707%	$256.2535	$256.25	$256.25	$256.30
Purchase #5	$47.78	7.659%	$51.4395	$51.44	$51.45	$51.40
Purchase #6	$208.80	13.568%	$237.13	$237.13	$237.15	$237.10
Purchase #7	$244.91	6.745%	$261.4292	$261.43	$261.45	$261.40
7 purchase totals =	$982.31		$1,069.5551	$1,069.55	$1,069.60	$1,069.60