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 $91.33   5.110%   $95.997   $96.00   $96.00   $96.00  
  Purchase #2 $188.39   7.252%   $202.052   $202.05   $202.05   $202.10  
  Purchase #3 $205.83   9.116%   $224.5935   $224.59   $224.60   $224.60  
  Purchase #4 $92.64   13.749%   $105.3771   $105.38   $105.40   $105.40  
  Purchase #5 $125.40   6.111%   $133.0632   $133.06   $133.05   $133.10  
  Purchase #6 $7.86   8.672%   $8.5416   $8.54   $8.55   $8.50  
  Purchase #7 $176.53   6.527%   $188.0521   $188.05   $188.05   $188.10  
  7 purchase totals = $887.98       $957.6765   $957.67   $957.70   $957.80