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 $86.97   9.193%   $94.9652   $94.97   $94.95   $95.00  
  Purchase #2 $34.93   11.787%   $39.0472   $39.05   $39.05   $39.00  
  Purchase #3 $12.92   11.723%   $14.4346   $14.43   $14.45   $14.40  
  Purchase #4 $250.72   9.488%   $274.5083   $274.51   $274.50   $274.50  
  Purchase #5 $118.28   13.674%   $134.4536   $134.45   $134.45   $134.50  
  Purchase #6 $30.43   9.321%   $33.2664   $33.27   $33.25   $33.30  
  Purchase #7 $186.87   6.158%   $198.3775   $198.38   $198.40   $198.40  
  7 purchase totals = $721.12       $789.0528   $789.06   $789.05   $789.10