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 $60.39   7.115%   $64.6867   $64.69   $64.70   $64.70  
  Purchase #2 $217.41   10.115%   $239.401   $239.40   $239.40   $239.40  
  Purchase #3 $237.49   11.179%   $264.039   $264.04   $264.05   $264.00  
  Purchase #4 $161.76   11.834%   $180.9027   $180.90   $180.90   $180.90  
  Purchase #5 $215.27   13.640%   $244.6328   $244.63   $244.65   $244.60  
  Purchase #6 $92.47   12.104%   $103.6626   $103.66   $103.65   $103.70  
  Purchase #7 $101.67   3.314%   $105.0393   $105.04   $105.05   $105.00  
  7 purchase totals = $1,086.46       $1,202.3641   $1,202.36   $1,202.40   $1,202.30