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 $65.49   13.559%   $74.3698   $74.37   $74.35   $74.40  
  Purchase #2 $174.28   8.687%   $189.4197   $189.42   $189.40   $189.40  
  Purchase #3 $236.25   4.357%   $246.5434   $246.54   $246.55   $246.50  
  Purchase #4 $33.91   9.254%   $37.048   $37.05   $37.05   $37.00  
  Purchase #5 $221.94   9.307%   $242.596   $242.60   $242.60   $242.60  
  Purchase #6 $245.25   6.431%   $261.022   $261.02   $261.00   $261.00  
  Purchase #7 $196.54   5.808%   $207.955   $207.96   $207.95   $208.00  
  7 purchase totals = $1,173.66       $1,258.9539   $1,258.96   $1,258.90   $1,258.90