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	$131.88	5.445%	$139.0609	$139.06	$139.05	$139.10
Purchase #2	$124.56	5.276%	$131.1318	$131.13	$131.15	$131.10
Purchase #3	$68.63	5.841%	$72.6387	$72.64	$72.65	$72.60
Purchase #4	$246.45	13.275%	$279.1662	$279.17	$279.15	$279.20
Purchase #5	$222.52	10.587%	$246.0782	$246.08	$246.10	$246.10
Purchase #6	$118.84	11.156%	$132.0978	$132.10	$132.10	$132.10
Purchase #7	$225.86	3.294%	$233.2998	$233.30	$233.30	$233.30
7 purchase totals =	$1,138.74		$1,233.4734	$1,233.48	$1,233.50	$1,233.50