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 $38.44   7.603%   $41.3626   $41.36   $41.35   $41.40  
  Purchase #2 $182.66   7.358%   $196.1001   $196.10   $196.10   $196.10  
  Purchase #3 $123.57   11.458%   $137.7287   $137.73   $137.75   $137.70  
  Purchase #4 $86.32   6.512%   $91.9412   $91.94   $91.95   $91.90  
  Purchase #5 $48.84   5.722%   $51.6346   $51.63   $51.65   $51.60  
  Purchase #6 $158.77   4.872%   $166.5053   $166.51   $166.50   $166.50  
  Purchase #7 $15.33   5.706%   $16.2047   $16.20   $16.20   $16.20  
  7 purchase totals = $653.93       $701.4772   $701.47   $701.50   $701.40