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 $41.34   6.476%   $44.0172   $44.02   $44.00   $44.00  
  Purchase #2 $232.49   5.623%   $245.5629   $245.56   $245.55   $245.60  
  Purchase #3 $248.57   12.846%   $280.5013   $280.50   $280.50   $280.50  
  Purchase #4 $249.91   6.690%   $266.629   $266.63   $266.65   $266.60  
  Purchase #5 $75.81   8.850%   $82.5192   $82.52   $82.50   $82.50  
  Purchase #6 $221.99   4.629%   $232.2659   $232.27   $232.25   $232.30  
  Purchase #7 $231.93   13.260%   $262.6839   $262.68   $262.70   $262.70  
  7 purchase totals = $1,302.04       $1,414.1794   $1,414.18   $1,414.15   $1,414.20