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 $213.71   8.730%   $232.3669   $232.37   $232.35   $232.40  
  Purchase #2 $116.89   6.328%   $124.2868   $124.29   $124.30   $124.30  
  Purchase #3 $69.27   10.628%   $76.632   $76.63   $76.65   $76.60  
  Purchase #4 $51.45   8.533%   $55.8402   $55.84   $55.85   $55.80  
  Purchase #5 $210.90   8.419%   $228.6557   $228.66   $228.65   $228.70  
  Purchase #6 $242.83   12.625%   $273.4873   $273.49   $273.50   $273.50  
  Purchase #7 $33.42   7.640%   $35.9733   $35.97   $35.95   $36.00  
  7 purchase totals = $938.47       $1,027.2422   $1,027.25   $1,027.25   $1,027.30