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 $206.99   13.520%   $234.975   $234.98   $235.00   $235.00  
  Purchase #2 $199.89   12.130%   $224.1367   $224.14   $224.15   $224.10  
  Purchase #3 $42.83   12.568%   $48.2129   $48.21   $48.20   $48.20  
  Purchase #4 $35.36   10.111%   $38.9352   $38.94   $38.95   $38.90  
  Purchase #5 $99.44   6.721%   $106.1234   $106.12   $106.10   $106.10  
  Purchase #6 $178.40   8.191%   $193.0127   $193.01   $193.00   $193.00  
  Purchase #7 $26.95   12.296%   $30.2638   $30.26   $30.25   $30.30  
  7 purchase totals = $789.86       $875.6597   $875.66   $875.65   $875.60