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 $208.36   13.146%   $235.751   $235.75   $235.75   $235.80  
  Purchase #2 $215.50   12.685%   $242.8362   $242.84   $242.85   $242.80  
  Purchase #3 $49.31   13.557%   $55.995   $56.00   $56.00   $56.00  
  Purchase #4 $94.78   13.698%   $107.763   $107.76   $107.75   $107.80  
  Purchase #5 $166.63   12.686%   $187.7687   $187.77   $187.75   $187.80  
  Purchase #6 $178.99   11.788%   $200.0893   $200.09   $200.10   $200.10  
  Purchase #7 $190.60   12.592%   $214.6004   $214.60   $214.60   $214.60  
  7 purchase totals = $1,104.17       $1,244.8036   $1,244.81   $1,244.80   $1,244.90