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	$57.82	6.163%	$61.3834	$61.38	$61.40	$61.40
Purchase #2	$184.34	3.226%	$190.2868	$190.29	$190.30	$190.30
Purchase #3	$176.68	6.631%	$188.3957	$188.40	$188.40	$188.40
Purchase #4	$199.88	6.296%	$212.4644	$212.46	$212.45	$212.50
Purchase #5	$97.62	6.221%	$103.6929	$103.69	$103.70	$103.70
Purchase #6	$95.56	7.766%	$102.9812	$102.98	$103.00	$103.00
Purchase #7	$9.90	10.590%	$10.9484	$10.95	$10.95	$10.90
7 purchase totals =	$821.80		$870.1528	$870.15	$870.20	$870.20