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	$133.95	10.690%	$148.2693	$148.27	$148.25	$148.30
Purchase #2	$225.62	8.633%	$245.0978	$245.10	$245.10	$245.10
Purchase #3	$82.46	5.660%	$87.1272	$87.13	$87.15	$87.10
Purchase #4	$144.31	10.143%	$158.9474	$158.95	$158.95	$158.90
Purchase #5	$63.97	5.333%	$67.3815	$67.38	$67.40	$67.40
Purchase #6	$198.37	12.189%	$222.5493	$222.55	$222.55	$222.50
Purchase #7	$234.48	10.496%	$259.091	$259.09	$259.10	$259.10
7 purchase totals =	$1,083.16		$1,188.4635	$1,188.47	$1,188.50	$1,188.40