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 $112.91   5.546%   $119.172   $119.17   $119.15   $119.20  
  Purchase #2 $202.61   12.323%   $227.5776   $227.58   $227.60   $227.60  
  Purchase #3 $57.95   5.347%   $61.0486   $61.05   $61.05   $61.00  
  Purchase #4 $38.71   6.648%   $41.2834   $41.28   $41.30   $41.30  
  Purchase #5 $85.30   12.175%   $95.6853   $95.69   $95.70   $95.70  
  Purchase #6 $206.56   12.274%   $231.9132   $231.91   $231.90   $231.90  
  Purchase #7 $206.86   5.509%   $218.2559   $218.26   $218.25   $218.30  
  7 purchase totals = $910.90       $994.9360   $994.94   $994.95   $995.00