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	$82.89	10.736%	$91.7891	$91.79	$91.80	$91.80
Purchase #2	$192.69	6.338%	$204.9027	$204.90	$204.90	$204.90
Purchase #3	$169.86	12.791%	$191.5868	$191.59	$191.60	$191.60
Purchase #4	$246.54	6.187%	$261.7934	$261.79	$261.80	$261.80
Purchase #5	$102.87	10.264%	$113.4286	$113.43	$113.45	$113.40
Purchase #6	$161.42	6.561%	$172.0108	$172.01	$172.00	$172.00
Purchase #7	$7.83	12.746%	$8.828	$8.83	$8.85	$8.80
7 purchase totals =	$964.10		$1,044.3394	$1,044.34	$1,044.40	$1,044.30