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 $119.26   6.241%   $126.703   $126.70   $126.70   $126.70  
  Purchase #2 $63.73   11.806%   $71.254   $71.25   $71.25   $71.30  
  Purchase #3 $201.28   13.869%   $229.1955   $229.20   $229.20   $229.20  
  Purchase #4 $209.69   11.375%   $233.5422   $233.54   $233.55   $233.50  
  Purchase #5 $181.56   5.477%   $191.504   $191.50   $191.50   $191.50  
  Purchase #6 $229.71   13.683%   $261.1412   $261.14   $261.15   $261.10  
  Purchase #7 $215.44   11.769%   $240.7951   $240.80   $240.80   $240.80  
  7 purchase totals = $1,220.67       $1,354.1350   $1,354.13   $1,354.15   $1,354.10