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 $143.31   9.275%   $156.602   $156.60   $156.60   $156.60  
  Purchase #2 $209.93   6.183%   $222.91   $222.91   $222.90   $222.90  
  Purchase #3 $91.37   13.226%   $103.4546   $103.45   $103.45   $103.50  
  Purchase #4 $188.54   11.253%   $209.7564   $209.76   $209.75   $209.80  
  Purchase #5 $242.34   10.206%   $267.0732   $267.07   $267.05   $267.10  
  Purchase #6 $238.93   12.529%   $268.8655   $268.87   $268.85   $268.90  
  Purchase #7 $218.28   8.149%   $236.0676   $236.07   $236.05   $236.10  
  7 purchase totals = $1,332.70       $1,464.7293   $1,464.73   $1,464.65   $1,464.90