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 $91.87   5.507%   $96.9293   $96.93   $96.95   $96.90  
  Purchase #2 $156.29   12.473%   $175.7841   $175.78   $175.80   $175.80  
  Purchase #3 $119.81   7.524%   $128.8245   $128.82   $128.80   $128.80  
  Purchase #4 $210.30   9.398%   $230.064   $230.06   $230.05   $230.10  
  Purchase #5 $193.82   10.524%   $214.2176   $214.22   $214.20   $214.20  
  Purchase #6 $231.94   12.708%   $261.4149   $261.41   $261.40   $261.40  
  Purchase #7 $232.60   10.381%   $256.7462   $256.75   $256.75   $256.70  
  7 purchase totals = $1,236.63       $1,363.9806   $1,363.97   $1,363.95   $1,363.90