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 $55.88   11.535%   $62.3258   $62.33   $62.35   $62.30  
  Purchase #2 $212.41   11.445%   $236.7203   $236.72   $236.70   $236.70  
  Purchase #3 $179.50   6.358%   $190.9126   $190.91   $190.90   $190.90  
  Purchase #4 $239.87   13.746%   $272.8425   $272.84   $272.85   $272.80  
  Purchase #5 $244.81   5.564%   $258.4312   $258.43   $258.45   $258.40  
  Purchase #6 $22.99   7.218%   $24.6494   $24.65   $24.65   $24.60  
  Purchase #7 $197.60   8.620%   $214.6331   $214.63   $214.65   $214.60  
  7 purchase totals = $1,153.06       $1,260.5149   $1,260.51   $1,260.55   $1,260.30