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 $213.48   5.371%   $224.946   $224.95   $224.95   $224.90  
  Purchase #2 $149.43   10.617%   $165.295   $165.30   $165.30   $165.30  
  Purchase #3 $9.61   6.122%   $10.1983   $10.20   $10.20   $10.20  
  Purchase #4 $221.99   8.871%   $241.6827   $241.68   $241.70   $241.70  
  Purchase #5 $170.57   11.499%   $190.1838   $190.18   $190.20   $190.20  
  Purchase #6 $50.49   6.151%   $53.5956   $53.60   $53.60   $53.60  
  Purchase #7 $113.46   10.579%   $125.4629   $125.46   $125.45   $125.50  
  7 purchase totals = $929.03       $1,011.3643   $1,011.37   $1,011.40   $1,011.40