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	$106.46	10.425%	$117.5585	$117.56	$117.55	$117.60
Purchase #2	$105.32	13.847%	$119.9037	$119.90	$119.90	$119.90
Purchase #3	$90.48	8.238%	$97.9337	$97.93	$97.95	$97.90
Purchase #4	$215.97	4.456%	$225.5936	$225.59	$225.60	$225.60
Purchase #5	$232.97	3.864%	$241.972	$241.97	$241.95	$242.00
Purchase #6	$68.49	5.577%	$72.3097	$72.31	$72.30	$72.30
Purchase #7	$128.89	13.536%	$146.3366	$146.34	$146.35	$146.30
7 purchase totals =	$948.58		$1,021.6078	$1,021.60	$1,021.60	$1,021.60