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 $186.27   5.743%   $196.9675   $196.97   $196.95   $197.00  
  Purchase #2 $208.78   6.484%   $222.3173   $222.32   $222.30   $222.30  
  Purchase #3 $246.39   6.687%   $262.8661   $262.87   $262.85   $262.90  
  Purchase #4 $69.99   9.847%   $76.8819   $76.88   $76.90   $76.90  
  Purchase #5 $63.42   9.705%   $69.5749   $69.57   $69.55   $69.60  
  Purchase #6 $245.64   3.695%   $254.7164   $254.72   $254.70   $254.70  
  Purchase #7 $22.75   11.258%   $25.3112   $25.31   $25.30   $25.30  
  7 purchase totals = $1,043.24       $1,108.6353   $1,108.64   $1,108.55   $1,108.70