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 $86.54   10.558%   $95.6769   $95.68   $95.70   $95.70  
  Purchase #2 $61.45   3.181%   $63.4047   $63.40   $63.40   $63.40  
  Purchase #3 $71.99   13.719%   $81.8663   $81.87   $81.85   $81.90  
  Purchase #4 $96.42   7.220%   $103.3815   $103.38   $103.40   $103.40  
  Purchase #5 $196.49   6.803%   $209.8572   $209.86   $209.85   $209.90  
  Purchase #6 $238.34   10.853%   $264.207   $264.21   $264.20   $264.20  
  Purchase #7 $164.25   11.166%   $182.5902   $182.59   $182.60   $182.60  
  7 purchase totals = $915.48       $1,000.9838   $1,000.99   $1,001.00   $1,001.10