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 $83.72   13.566%   $95.0775   $95.08   $95.10   $95.10  
  Purchase #2 $141.46   8.864%   $153.999   $154.00   $154.00   $154.00  
  Purchase #3 $18.81   4.801%   $19.7131   $19.71   $19.70   $19.70  
  Purchase #4 $151.66   12.116%   $170.0351   $170.04   $170.05   $170.00  
  Purchase #5 $157.72   8.829%   $171.6451   $171.65   $171.65   $171.60  
  Purchase #6 $37.80   12.659%   $42.5851   $42.59   $42.60   $42.60  
  Purchase #7 $43.27   10.193%   $47.6805   $47.68   $47.70   $47.70  
  7 purchase totals = $634.44       $700.7354   $700.75   $700.80   $700.70