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 $23.37   5.270%   $24.6016   $24.60   $24.60   $24.60  
  Purchase #2 $190.68   3.316%   $197.0029   $197.00   $197.00   $197.00  
  Purchase #3 $34.53   3.870%   $35.8663   $35.87   $35.85   $35.90  
  Purchase #4 $216.96   11.353%   $241.5915   $241.59   $241.60   $241.60  
  Purchase #5 $202.91   12.757%   $228.7952   $228.80   $228.80   $228.80  
  Purchase #6 $38.85   10.122%   $42.7824   $42.78   $42.80   $42.80  
  Purchase #7 $85.91   7.782%   $92.5955   $92.60   $92.60   $92.60  
  7 purchase totals = $793.21       $863.2354   $863.24   $863.25   $863.30