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 $56.38   11.332%   $62.769   $62.77   $62.75   $62.80  
  Purchase #2 $52.84   4.335%   $55.1306   $55.13   $55.15   $55.10  
  Purchase #3 $69.75   5.445%   $73.5479   $73.55   $73.55   $73.50  
  Purchase #4 $214.61   10.369%   $236.8629   $236.86   $236.85   $236.90  
  Purchase #5 $94.88   12.724%   $106.9525   $106.95   $106.95   $107.00  
  Purchase #6 $50.81   13.377%   $57.6069   $57.61   $57.60   $57.60  
  Purchase #7 $171.37   8.216%   $185.4498   $185.45   $185.45   $185.40  
  7 purchase totals = $710.64       $778.3196   $778.32   $778.30   $778.30