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 $61.94   8.519%   $67.2167   $67.22   $67.20   $67.20  
  Purchase #2 $214.91   7.842%   $231.7632   $231.76   $231.75   $231.80  
  Purchase #3 $244.34   5.854%   $258.6437   $258.64   $258.65   $258.60  
  Purchase #4 $163.63   7.818%   $176.4226   $176.42   $176.40   $176.40  
  Purchase #5 $239.72   4.233%   $249.8673   $249.87   $249.85   $249.90  
  Purchase #6 $48.91   3.720%   $50.7295   $50.73   $50.75   $50.70  
  Purchase #7 $84.75   8.207%   $91.7054   $91.71   $91.70   $91.70  
  7 purchase totals = $1,058.20       $1,126.3484   $1,126.35   $1,126.30   $1,126.30