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 $173.25   13.197%   $196.1138   $196.11   $196.10   $196.10  
  Purchase #2 $69.95   5.134%   $73.5412   $73.54   $73.55   $73.50  
  Purchase #3 $92.94   5.361%   $97.9225   $97.92   $97.90   $97.90  
  Purchase #4 $43.92   3.427%   $45.4251   $45.43   $45.45   $45.40  
  Purchase #5 $159.81   13.300%   $181.0647   $181.06   $181.05   $181.10  
  Purchase #6 $238.28   6.747%   $254.3568   $254.36   $254.35   $254.40  
  Purchase #7 $112.92   10.317%   $124.57   $124.57   $124.55   $124.60  
  7 purchase totals = $891.07       $972.9941   $972.99   $972.95   $973.00