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 $92.67   13.328%   $105.0211   $105.02   $105.00   $105.00  
  Purchase #2 $247.25   4.632%   $258.7026   $258.70   $258.70   $258.70  
  Purchase #3 $69.26   13.706%   $78.7528   $78.75   $78.75   $78.80  
  Purchase #4 $36.67   6.110%   $38.9105   $38.91   $38.90   $38.90  
  Purchase #5 $240.80   8.350%   $260.9068   $260.91   $260.90   $260.90  
  Purchase #6 $110.49   9.836%   $121.3578   $121.36   $121.35   $121.40  
  Purchase #7 $176.79   6.833%   $188.8701   $188.87   $188.85   $188.90  
  7 purchase totals = $973.93       $1,052.5217   $1,052.52   $1,052.45   $1,052.60