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 $103.81   10.760%   $114.98   $114.98   $115.00   $115.00  
  Purchase #2 $86.56   8.874%   $94.2413   $94.24   $94.25   $94.20  
  Purchase #3 $154.63   12.595%   $174.1056   $174.11   $174.10   $174.10  
  Purchase #4 $210.78   3.312%   $217.761   $217.76   $217.75   $217.80  
  Purchase #5 $249.36   6.497%   $265.5609   $265.56   $265.55   $265.60  
  Purchase #6 $154.82   13.348%   $175.4854   $175.49   $175.50   $175.50  
  Purchase #7 $7.39   5.359%   $7.786   $7.79   $7.80   $7.80  
  7 purchase totals = $967.35       $1,049.9202   $1,049.93   $1,049.95   $1,050.00