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 $86.77   8.382%   $94.0431   $94.04   $94.05   $94.00  
  Purchase #2 $242.77   7.280%   $260.4437   $260.44   $260.45   $260.40  
  Purchase #3 $46.52   8.666%   $50.5514   $50.55   $50.55   $50.60  
  Purchase #4 $90.31   3.474%   $93.4474   $93.45   $93.45   $93.40  
  Purchase #5 $188.67   11.452%   $210.2765   $210.28   $210.30   $210.30  
  Purchase #6 $162.65   5.269%   $171.22   $171.22   $171.20   $171.20  
  Purchase #7 $180.81   8.542%   $196.2548   $196.25   $196.25   $196.30  
  7 purchase totals = $998.50       $1,076.2369   $1,076.23   $1,076.25   $1,076.20