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 $197.91   9.526%   $216.7629   $216.76   $216.75   $216.80  
  Purchase #2 $15.71   8.839%   $17.0986   $17.10   $17.10   $17.10  
  Purchase #3 $224.42   11.704%   $250.6861   $250.69   $250.70   $250.70  
  Purchase #4 $63.89   5.349%   $67.3075   $67.31   $67.30   $67.30  
  Purchase #5 $207.62   13.465%   $235.576   $235.58   $235.60   $235.60  
  Purchase #6 $67.73   12.102%   $75.9267   $75.93   $75.95   $75.90  
  Purchase #7 $172.91   5.601%   $182.5947   $182.59   $182.60   $182.60  
  7 purchase totals = $950.19       $1,045.9525   $1,045.96   $1,046.00   $1,046.00