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 $158.75   10.861%   $175.9918   $175.99   $176.00   $176.00  
  Purchase #2 $188.88   6.508%   $201.1723   $201.17   $201.15   $201.20  
  Purchase #3 $24.31   5.338%   $25.6077   $25.61   $25.60   $25.60  
  Purchase #4 $62.54   11.818%   $69.931   $69.93   $69.95   $69.90  
  Purchase #5 $217.86   4.860%   $228.448   $228.45   $228.45   $228.40  
  Purchase #6 $36.72   4.494%   $38.3702   $38.37   $38.35   $38.40  
  Purchase #7 $14.37   9.376%   $15.7173   $15.72   $15.70   $15.70  
  7 purchase totals = $703.43       $755.2383   $755.24   $755.20   $755.20