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 $205.48   5.410%   $216.5965   $216.60   $216.60   $216.60  
  Purchase #2 $249.39   7.328%   $267.6653   $267.67   $267.65   $267.70  
  Purchase #3 $185.34   11.569%   $206.782   $206.78   $206.80   $206.80  
  Purchase #4 $214.35   6.337%   $227.9334   $227.93   $227.95   $227.90  
  Purchase #5 $149.57   5.364%   $157.5929   $157.59   $157.60   $157.60  
  Purchase #6 $13.29   7.839%   $14.3318   $14.33   $14.35   $14.30  
  Purchase #7 $104.81   8.586%   $113.809   $113.81   $113.80   $113.80  
  7 purchase totals = $1,122.23       $1,204.7109   $1,204.71   $1,204.75   $1,204.70