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 $69.66   3.264%   $71.9337   $71.93   $71.95   $71.90  
  Purchase #2 $118.45   9.283%   $129.4457   $129.45   $129.45   $129.40  
  Purchase #3 $124.84   5.342%   $131.509   $131.51   $131.50   $131.50  
  Purchase #4 $183.78   4.181%   $191.4638   $191.46   $191.45   $191.50  
  Purchase #5 $193.90   7.247%   $207.9519   $207.95   $207.95   $208.00  
  Purchase #6 $201.79   11.599%   $225.1956   $225.20   $225.20   $225.20  
  Purchase #7 $53.87   8.665%   $58.5378   $58.54   $58.55   $58.50  
  7 purchase totals = $946.29       $1,016.0375   $1,016.04   $1,016.05   $1,016.00