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	$59.41	6.804%	$63.4523	$63.45	$63.45	$63.50
Purchase #2	$90.73	13.746%	$103.2017	$103.20	$103.20	$103.20
Purchase #3	$86.43	3.676%	$89.6072	$89.61	$89.60	$89.60
Purchase #4	$231.77	4.497%	$242.1927	$242.19	$242.20	$242.20
Purchase #5	$167.80	5.634%	$177.2539	$177.25	$177.25	$177.30
Purchase #6	$61.81	7.728%	$66.5867	$66.59	$66.60	$66.60
Purchase #7	$213.82	3.168%	$220.5938	$220.59	$220.60	$220.60
7 purchase totals =	$911.77		$962.8883	$962.88	$962.90	$963.00