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 $63.25   7.771%   $68.1652   $68.17   $68.15   $68.20  
  Purchase #2 $199.27   13.228%   $225.6294   $225.63   $225.65   $225.60  
  Purchase #3 $224.99   9.857%   $247.1673   $247.17   $247.15   $247.20  
  Purchase #4 $175.91   12.791%   $198.4106   $198.41   $198.40   $198.40  
  Purchase #5 $232.75   10.834%   $257.9661   $257.97   $257.95   $258.00  
  Purchase #6 $32.70   8.669%   $35.5348   $35.53   $35.55   $35.50  
  Purchase #7 $75.37   8.346%   $81.6604   $81.66   $81.65   $81.70  
  7 purchase totals = $1,004.24       $1,114.5338   $1,114.54   $1,114.50   $1,114.60