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 $114.26   3.599%   $118.3722   $118.37   $118.35   $118.40  
  Purchase #2 $233.90   13.444%   $265.3455   $265.35   $265.35   $265.30  
  Purchase #3 $196.63   5.531%   $207.5056   $207.51   $207.50   $207.50  
  Purchase #4 $187.46   7.432%   $201.392   $201.39   $201.40   $201.40  
  Purchase #5 $62.78   9.299%   $68.6179   $68.62   $68.60   $68.60  
  Purchase #6 $172.55   8.295%   $186.863   $186.86   $186.85   $186.90  
  Purchase #7 $133.42   10.850%   $147.8961   $147.90   $147.90   $147.90  
  7 purchase totals = $1,101.00       $1,195.9923   $1,196.00   $1,195.95   $1,196.00