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	$135.26	4.857%	$141.8296	$141.83	$141.85	$141.80
Purchase #2	$85.73	13.239%	$97.0798	$97.08	$97.10	$97.10
Purchase #3	$37.81	6.142%	$40.1323	$40.13	$40.15	$40.10
Purchase #4	$250.97	11.712%	$280.3636	$280.36	$280.35	$280.40
Purchase #5	$159.74	6.166%	$169.5896	$169.59	$169.60	$169.60
Purchase #6	$205.28	4.630%	$214.7845	$214.78	$214.80	$214.80
Purchase #7	$137.31	4.355%	$143.2899	$143.29	$143.30	$143.30
7 purchase totals =	$1,012.10		$1,087.0693	$1,087.06	$1,087.15	$1,087.10