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 $246.70   6.182%   $261.951   $261.95   $261.95   $262.00  
  Purchase #2 $79.63   8.326%   $86.26   $86.26   $86.25   $86.30  
  Purchase #3 $245.54   11.492%   $273.7575   $273.76   $273.75   $273.80  
  Purchase #4 $116.52   10.758%   $129.0552   $129.06   $129.05   $129.10  
  Purchase #5 $81.87   8.447%   $88.7856   $88.79   $88.80   $88.80  
  Purchase #6 $177.51   13.351%   $201.2094   $201.21   $201.20   $201.20  
  Purchase #7 $130.91   12.191%   $146.8692   $146.87   $146.85   $146.90  
  7 purchase totals = $1,078.68       $1,187.8879   $1,187.90   $1,187.85   $1,188.10