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 $91.49   5.543%   $96.5613   $96.56   $96.55   $96.60  
  Purchase #2 $167.30   7.295%   $179.5045   $179.50   $179.50   $179.50  
  Purchase #3 $225.45   7.190%   $241.6599   $241.66   $241.65   $241.70  
  Purchase #4 $176.57   12.662%   $198.9273   $198.93   $198.95   $198.90  
  Purchase #5 $38.44   3.264%   $39.6947   $39.69   $39.70   $39.70  
  Purchase #6 $93.49   4.303%   $97.5129   $97.51   $97.50   $97.50  
  Purchase #7 $88.95   13.632%   $101.0757   $101.08   $101.10   $101.10  
  7 purchase totals = $881.69       $954.9363   $954.93   $954.95   $955.00