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 $83.84   13.301%   $94.9916   $94.99   $95.00   $95.00  
  Purchase #2 $145.85   6.315%   $155.0604   $155.06   $155.05   $155.10  
  Purchase #3 $241.77   7.720%   $260.4346   $260.43   $260.45   $260.40  
  Purchase #4 $17.81   10.778%   $19.7296   $19.73   $19.75   $19.70  
  Purchase #5 $216.70   11.794%   $242.2576   $242.26   $242.25   $242.30  
  Purchase #6 $183.88   6.616%   $196.0455   $196.05   $196.05   $196.00  
  Purchase #7 $250.95   7.688%   $270.243   $270.24   $270.25   $270.20  
  7 purchase totals = $1,140.80       $1,238.7623   $1,238.76   $1,238.80   $1,238.70