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 $176.84   10.815%   $195.9652   $195.97   $195.95   $196.00  
  Purchase #2 $250.88   7.448%   $269.5655   $269.57   $269.55   $269.60  
  Purchase #3 $27.42   9.411%   $30.0005   $30.00   $30.00   $30.00  
  Purchase #4 $87.34   13.606%   $99.2235   $99.22   $99.20   $99.20  
  Purchase #5 $165.86   13.344%   $187.9924   $187.99   $188.00   $188.00  
  Purchase #6 $225.70   4.690%   $236.2853   $236.29   $236.30   $236.30  
  Purchase #7 $200.67   3.602%   $207.8981   $207.90   $207.90   $207.90  
  7 purchase totals = $1,134.71       $1,226.9305   $1,226.94   $1,226.90   $1,227.00