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	$103.92	9.395%	$113.6833	$113.68	$113.70	$113.70
Purchase #2	$66.80	7.856%	$72.0478	$72.05	$72.05	$72.00
Purchase #3	$189.81	5.577%	$200.3957	$200.40	$200.40	$200.40
Purchase #4	$234.94	5.311%	$247.4177	$247.42	$247.40	$247.40
Purchase #5	$90.79	13.727%	$103.2527	$103.25	$103.25	$103.30
Purchase #6	$75.90	10.164%	$83.6145	$83.61	$83.60	$83.60
Purchase #7	$206.52	4.502%	$215.8175	$215.82	$215.80	$215.80
7 purchase totals =	$968.68		$1,036.2292	$1,036.23	$1,036.20	$1,036.20