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 $195.62   5.262%   $205.9135   $205.91   $205.90   $205.90  
  Purchase #2 $69.66   12.806%   $78.5807   $78.58   $78.60   $78.60  
  Purchase #3 $220.94   12.275%   $248.0604   $248.06   $248.05   $248.10  
  Purchase #4 $197.92   13.464%   $224.5679   $224.57   $224.55   $224.60  
  Purchase #5 $192.89   12.466%   $216.9357   $216.94   $216.95   $216.90  
  Purchase #6 $24.62   7.648%   $26.5029   $26.50   $26.50   $26.50  
  Purchase #7 $199.71   5.255%   $210.2048   $210.20   $210.20   $210.20  
  7 purchase totals = $1,101.36       $1,210.7659   $1,210.76   $1,210.75   $1,210.80