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	$143.96	5.460%	$151.8202	$151.82	$151.80	$151.80
Purchase #2	$208.70	3.245%	$215.4723	$215.47	$215.45	$215.50
Purchase #3	$40.30	12.853%	$45.4798	$45.48	$45.50	$45.50
Purchase #4	$185.83	3.358%	$192.0702	$192.07	$192.05	$192.10
Purchase #5	$28.67	3.239%	$29.5986	$29.60	$29.60	$29.60
Purchase #6	$246.59	10.855%	$273.3573	$273.36	$273.35	$273.40
Purchase #7	$38.31	4.561%	$40.0573	$40.06	$40.05	$40.10
7 purchase totals =	$892.36		$947.8557	$947.86	$947.80	$948.00