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 $56.36   11.474%   $62.8267   $62.83   $62.85   $62.80  
  Purchase #2 $168.30   4.305%   $175.5453   $175.55   $175.55   $175.50  
  Purchase #3 $224.70   5.340%   $236.699   $236.70   $236.70   $236.70  
  Purchase #4 $9.80   8.282%   $10.6116   $10.61   $10.60   $10.60  
  Purchase #5 $61.48   4.711%   $64.3763   $64.38   $64.40   $64.40  
  Purchase #6 $182.32   13.374%   $206.7035   $206.70   $206.70   $206.70  
  Purchase #7 $181.89   13.696%   $206.8017   $206.80   $206.80   $206.80  
  7 purchase totals = $884.85       $963.5641   $963.57   $963.60   $963.50