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 $60.49   11.285%   $67.3163   $67.32   $67.30   $67.30  
  Purchase #2 $191.86   5.449%   $202.3145   $202.31   $202.30   $202.30  
  Purchase #3 $163.78   4.679%   $171.4433   $171.44   $171.45   $171.40  
  Purchase #4 $181.72   7.340%   $195.0582   $195.06   $195.05   $195.10  
  Purchase #5 $214.34   9.605%   $234.9274   $234.93   $234.95   $234.90  
  Purchase #6 $68.87   9.217%   $75.2177   $75.22   $75.20   $75.20  
  Purchase #7 $234.63   9.288%   $256.4224   $256.42   $256.40   $256.40  
  7 purchase totals = $1,115.69       $1,202.6998   $1,202.70   $1,202.65   $1,202.60