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 $33.63   7.493%   $36.1499   $36.15   $36.15   $36.10  
  Purchase #2 $245.82   7.665%   $264.6621   $264.66   $264.65   $264.70  
  Purchase #3 $60.95   3.815%   $63.2752   $63.28   $63.30   $63.30  
  Purchase #4 $72.99   9.626%   $80.016   $80.02   $80.00   $80.00  
  Purchase #5 $201.33   11.605%   $224.6943   $224.69   $224.70   $224.70  
  Purchase #6 $233.66   9.692%   $256.3063   $256.31   $256.30   $256.30  
  Purchase #7 $190.67   9.566%   $208.9095   $208.91   $208.90   $208.90  
  7 purchase totals = $1,039.05       $1,134.0133   $1,134.02   $1,134.00   $1,134.00