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 $62.64   7.323%   $67.2271   $67.23   $67.25   $67.20  
  Purchase #2 $95.85   9.234%   $104.7008   $104.70   $104.70   $104.70  
  Purchase #3 $124.63   7.637%   $134.148   $134.15   $134.15   $134.10  
  Purchase #4 $162.71   12.291%   $182.7087   $182.71   $182.70   $182.70  
  Purchase #5 $178.96   12.742%   $201.7631   $201.76   $201.75   $201.80  
  Purchase #6 $71.53   3.533%   $74.0572   $74.06   $74.05   $74.10  
  Purchase #7 $115.61   7.134%   $123.8576   $123.86   $123.85   $123.90  
  7 purchase totals = $811.93       $888.4625   $888.47   $888.45   $888.50