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 $103.68   10.202%   $114.2574   $114.26   $114.25   $114.30  
  Purchase #2 $107.50   12.701%   $121.1536   $121.15   $121.15   $121.20  
  Purchase #3 $209.30   11.173%   $232.6851   $232.69   $232.70   $232.70  
  Purchase #4 $227.41   3.869%   $236.2085   $236.21   $236.20   $236.20  
  Purchase #5 $137.63   9.637%   $150.8934   $150.89   $150.90   $150.90  
  Purchase #6 $205.60   6.245%   $218.4397   $218.44   $218.45   $218.40  
  Purchase #7 $203.39   9.595%   $222.9053   $222.91   $222.90   $222.90  
  7 purchase totals = $1,194.51       $1,296.5430   $1,296.55   $1,296.55   $1,296.60