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 $95.91   12.550%   $107.9467   $107.95   $107.95   $107.90  
  Purchase #2 $174.92   8.814%   $190.3374   $190.34   $190.35   $190.30  
  Purchase #3 $118.35   3.630%   $122.6461   $122.65   $122.65   $122.60  
  Purchase #4 $239.62   7.869%   $258.4757   $258.48   $258.50   $258.50  
  Purchase #5 $188.85   7.609%   $203.2196   $203.22   $203.20   $203.20  
  Purchase #6 $176.45   12.336%   $198.2169   $198.22   $198.20   $198.20  
  Purchase #7 $82.33   9.807%   $90.4041   $90.40   $90.40   $90.40  
  7 purchase totals = $1,076.43       $1,171.2465   $1,171.26   $1,171.25   $1,171.10