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	$131.34	12.267%	$147.4515	$147.45	$147.45	$147.50
Purchase #2	$151.31	11.393%	$168.5487	$168.55	$168.55	$168.50
Purchase #3	$92.92	13.709%	$105.6584	$105.66	$105.65	$105.70
Purchase #4	$111.83	9.822%	$122.8139	$122.81	$122.80	$122.80
Purchase #5	$81.42	4.410%	$85.0106	$85.01	$85.00	$85.00
Purchase #6	$189.63	4.703%	$198.5483	$198.55	$198.55	$198.50
Purchase #7	$214.29	11.564%	$239.0705	$239.07	$239.05	$239.10
7 purchase totals =	$972.74		$1,067.1019	$1,067.10	$1,067.05	$1,067.10