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	$205.77	9.261%	$224.8264	$224.83	$224.85	$224.80
Purchase #2	$135.88	4.445%	$141.9199	$141.92	$141.90	$141.90
Purchase #3	$54.42	8.423%	$59.0038	$59.00	$59.00	$59.00
Purchase #4	$103.49	13.350%	$117.3059	$117.31	$117.30	$117.30
Purchase #5	$42.74	8.401%	$46.3306	$46.33	$46.35	$46.30
Purchase #6	$77.86	7.776%	$83.9144	$83.91	$83.90	$83.90
Purchase #7	$101.55	12.771%	$114.519	$114.52	$114.50	$114.50
7 purchase totals =	$721.71		$787.8200	$787.82	$787.80	$787.70