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 $53.83   13.427%   $61.0578   $61.06   $61.05   $61.10  
  Purchase #2 $192.82   6.176%   $204.7286   $204.73   $204.75   $204.70  
  Purchase #3 $117.55   13.193%   $133.0584   $133.06   $133.05   $133.10  
  Purchase #4 $90.66   3.343%   $93.6908   $93.69   $93.70   $93.70  
  Purchase #5 $97.53   13.152%   $110.3571   $110.36   $110.35   $110.40  
  Purchase #6 $230.48   13.324%   $261.1892   $261.19   $261.20   $261.20  
  Purchase #7 $101.95   9.223%   $111.3528   $111.35   $111.35   $111.40  
  7 purchase totals = $884.82       $975.4347   $975.44   $975.45   $975.60