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	$235.87	10.461%	$260.5444	$260.54	$260.55	$260.50
Purchase #2	$240.42	13.334%	$272.4776	$272.48	$272.50	$272.50
Purchase #3	$75.31	4.761%	$78.8955	$78.90	$78.90	$78.90
Purchase #4	$176.34	7.102%	$188.8637	$188.86	$188.85	$188.90
Purchase #5	$180.98	10.721%	$200.3829	$200.38	$200.40	$200.40
Purchase #6	$136.48	5.545%	$144.0478	$144.05	$144.05	$144.00
Purchase #7	$57.75	4.464%	$60.328	$60.33	$60.35	$60.30
7 purchase totals =	$1,103.15		$1,205.5399	$1,205.54	$1,205.60	$1,205.50