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	$208.99	13.650%	$237.5171	$237.52	$237.50	$237.50
Purchase #2	$199.55	7.648%	$214.8116	$214.81	$214.80	$214.80
Purchase #3	$126.25	11.571%	$140.8584	$140.86	$140.85	$140.90
Purchase #4	$35.37	7.622%	$38.0659	$38.07	$38.05	$38.10
Purchase #5	$224.43	7.595%	$241.4755	$241.48	$241.50	$241.50
Purchase #6	$90.66	12.291%	$101.803	$101.80	$101.80	$101.80
Purchase #7	$39.59	6.186%	$42.039	$42.04	$42.05	$42.00
7 purchase totals =	$924.84		$1,016.5705	$1,016.58	$1,016.55	$1,016.60