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 $196.84   4.779%   $206.247   $206.25   $206.25   $206.20  
  Purchase #2 $140.51   4.395%   $146.6854   $146.69   $146.70   $146.70  
  Purchase #3 $242.89   4.434%   $253.6597   $253.66   $253.65   $253.70  
  Purchase #4 $91.50   11.474%   $101.9987   $102.00   $102.00   $102.00  
  Purchase #5 $115.43   13.325%   $130.811   $130.81   $130.80   $130.80  
  Purchase #6 $151.94   4.627%   $158.9703   $158.97   $158.95   $159.00  
  Purchase #7 $138.37   13.603%   $157.1925   $157.19   $157.20   $157.20  
  7 purchase totals = $1,077.48       $1,155.5646   $1,155.57   $1,155.55   $1,155.60