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 $186.98   4.847%   $196.0429   $196.04   $196.05   $196.00  
  Purchase #2 $218.85   8.387%   $237.2049   $237.20   $237.20   $237.20  
  Purchase #3 $33.86   6.638%   $36.1076   $36.11   $36.10   $36.10  
  Purchase #4 $123.44   3.213%   $127.4061   $127.41   $127.40   $127.40  
  Purchase #5 $198.88   4.724%   $208.2751   $208.28   $208.30   $208.30  
  Purchase #6 $100.29   13.208%   $113.5363   $113.54   $113.55   $113.50  
  Purchase #7 $113.79   9.660%   $124.7821   $124.78   $124.80   $124.80  
  7 purchase totals = $976.09       $1,043.3550   $1,043.36   $1,043.40   $1,043.30