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 $41.61   7.261%   $44.6313   $44.63   $44.65   $44.60  
  Purchase #2 $137.59   12.615%   $154.947   $154.95   $154.95   $154.90  
  Purchase #3 $57.63   6.143%   $61.1702   $61.17   $61.15   $61.20  
  Purchase #4 $187.70   5.234%   $197.5242   $197.52   $197.50   $197.50  
  Purchase #5 $60.82   12.630%   $68.5016   $68.50   $68.50   $68.50  
  Purchase #6 $191.42   8.362%   $207.4265   $207.43   $207.45   $207.40  
  Purchase #7 $107.94   8.739%   $117.3729   $117.37   $117.35   $117.40  
  7 purchase totals = $784.71       $851.5737   $851.57   $851.55   $851.50