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 $208.28   12.367%   $234.038   $234.04   $234.05   $234.00  
  Purchase #2 $79.48   7.353%   $85.3242   $85.32   $85.30   $85.30  
  Purchase #3 $211.66   12.428%   $237.9651   $237.97   $237.95   $238.00  
  Purchase #4 $66.70   9.433%   $72.9918   $72.99   $73.00   $73.00  
  Purchase #5 $147.53   5.852%   $156.1635   $156.16   $156.15   $156.20  
  Purchase #6 $94.61   8.724%   $102.8638   $102.86   $102.85   $102.90  
  Purchase #7 $147.92   11.310%   $164.6498   $164.65   $164.65   $164.60  
  7 purchase totals = $956.18       $1,053.9962   $1,053.99   $1,053.95   $1,054.00