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 $185.76   8.769%   $202.0493   $202.05   $202.05   $202.00  
  Purchase #2 $94.56   11.342%   $105.285   $105.29   $105.30   $105.30  
  Purchase #3 $68.93   6.869%   $73.6648   $73.66   $73.65   $73.70  
  Purchase #4 $217.81   5.204%   $229.1448   $229.14   $229.15   $229.10  
  Purchase #5 $230.45   12.783%   $259.9084   $259.91   $259.90   $259.90  
  Purchase #6 $244.92   13.318%   $277.5384   $277.54   $277.55   $277.50  
  Purchase #7 $14.88   10.457%   $16.436   $16.44   $16.45   $16.40  
  7 purchase totals = $1,057.31       $1,164.0267   $1,164.03   $1,164.05   $1,163.90