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 $67.28   6.472%   $71.6344   $71.63   $71.65   $71.60  
  Purchase #2 $148.34   4.604%   $155.1696   $155.17   $155.15   $155.20  
  Purchase #3 $183.64   7.685%   $197.7527   $197.75   $197.75   $197.80  
  Purchase #4 $226.65   10.161%   $249.6799   $249.68   $249.70   $249.70  
  Purchase #5 $10.82   5.848%   $11.4528   $11.45   $11.45   $11.50  
  Purchase #6 $173.47   12.186%   $194.6091   $194.61   $194.60   $194.60  
  Purchase #7 $243.46   12.241%   $273.2619   $273.26   $273.25   $273.30  
  7 purchase totals = $1,053.66       $1,153.5604   $1,153.55   $1,153.55   $1,153.70