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	$126.80	7.617%	$136.4584	$136.46	$136.45	$136.50
Purchase #2	$154.83	6.527%	$164.9358	$164.94	$164.95	$164.90
Purchase #3	$30.92	5.721%	$32.6889	$32.69	$32.70	$32.70
Purchase #4	$234.89	6.562%	$250.3035	$250.30	$250.30	$250.30
Purchase #5	$197.86	4.268%	$206.3047	$206.30	$206.30	$206.30
Purchase #6	$35.26	12.421%	$39.6396	$39.64	$39.65	$39.60
Purchase #7	$225.96	12.855%	$255.0072	$255.01	$255.00	$255.00
7 purchase totals =	$1,006.52		$1,085.3381	$1,085.34	$1,085.35	$1,085.30