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	$51.53	10.180%	$56.7758	$56.78	$56.80	$56.80
Purchase #2	$83.47	12.425%	$93.8411	$93.84	$93.85	$93.80
Purchase #3	$107.28	6.796%	$114.5707	$114.57	$114.55	$114.60
Purchase #4	$117.98	4.579%	$123.3823	$123.38	$123.40	$123.40
Purchase #5	$224.69	6.169%	$238.5511	$238.55	$238.55	$238.60
Purchase #6	$136.87	4.398%	$142.8895	$142.89	$142.90	$142.90
Purchase #7	$233.37	13.799%	$265.5727	$265.57	$265.55	$265.60
7 purchase totals =	$955.19		$1,035.5832	$1,035.58	$1,035.60	$1,035.70