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 $214.27   10.638%   $237.064   $237.06   $237.05   $237.10  
  Purchase #2 $215.31   12.317%   $241.8297   $241.83   $241.85   $241.80  
  Purchase #3 $177.98   7.271%   $190.9209   $190.92   $190.90   $190.90  
  Purchase #4 $7.77   4.143%   $8.0919   $8.09   $8.10   $8.10  
  Purchase #5 $165.58   12.678%   $186.5722   $186.57   $186.55   $186.60  
  Purchase #6 $110.34   4.713%   $115.5403   $115.54   $115.55   $115.50  
  Purchase #7 $76.66   9.340%   $83.82   $83.82   $83.80   $83.80  
  7 purchase totals = $967.91       $1,063.8390   $1,063.83   $1,063.80   $1,063.80