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 $56.74   9.188%   $61.9533   $61.95   $61.95   $62.00  
  Purchase #2 $93.72   12.490%   $105.4256   $105.43   $105.45   $105.40  
  Purchase #3 $113.67   11.370%   $126.5943   $126.59   $126.60   $126.60  
  Purchase #4 $191.65   10.454%   $211.6851   $211.69   $211.70   $211.70  
  Purchase #5 $139.88   4.837%   $146.646   $146.65   $146.65   $146.60  
  Purchase #6 $237.84   12.850%   $268.4024   $268.40   $268.40   $268.40  
  Purchase #7 $122.99   11.800%   $137.5028   $137.50   $137.50   $137.50  
  7 purchase totals = $956.49       $1,058.2095   $1,058.21   $1,058.25   $1,058.20