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	$203.64	5.792%	$215.4348	$215.43	$215.45	$215.40
Purchase #2	$172.73	13.477%	$196.0088	$196.01	$196.00	$196.00
Purchase #3	$48.30	5.398%	$50.9072	$50.91	$50.90	$50.90
Purchase #4	$168.71	8.197%	$182.5392	$182.54	$182.55	$182.50
Purchase #5	$95.72	8.469%	$103.8265	$103.83	$103.85	$103.80
Purchase #6	$96.53	13.727%	$109.7807	$109.78	$109.80	$109.80
Purchase #7	$134.93	9.827%	$148.1896	$148.19	$148.20	$148.20
7 purchase totals =	$920.56		$1,006.6868	$1,006.69	$1,006.75	$1,006.60