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 $69.76   4.748%   $73.0722   $73.07   $73.05   $73.10  
  Purchase #2 $175.51   9.287%   $191.8096   $191.81   $191.80   $191.80  
  Purchase #3 $110.48   7.138%   $118.3661   $118.37   $118.35   $118.40  
  Purchase #4 $241.86   3.599%   $250.5645   $250.56   $250.55   $250.60  
  Purchase #5 $64.57   12.534%   $72.6632   $72.66   $72.65   $72.70  
  Purchase #6 $205.58   11.776%   $229.7891   $229.79   $229.80   $229.80  
  Purchase #7 $109.51   11.856%   $122.4935   $122.49   $122.50   $122.50  
  7 purchase totals = $977.27       $1,058.7582   $1,058.75   $1,058.70   $1,058.90