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 $214.64   5.773%   $227.0312   $227.03   $227.05   $227.00  
  Purchase #2 $67.95   4.148%   $70.7686   $70.77   $70.75   $70.80  
  Purchase #3 $70.65   3.408%   $73.0578   $73.06   $73.05   $73.10  
  Purchase #4 $117.68   3.366%   $121.6411   $121.64   $121.65   $121.60  
  Purchase #5 $38.66   10.314%   $42.6474   $42.65   $42.65   $42.60  
  Purchase #6 $249.41   4.207%   $259.9027   $259.90   $259.90   $259.90  
  Purchase #7 $218.64   5.560%   $230.7964   $230.80   $230.80   $230.80  
  7 purchase totals = $977.63       $1,025.8452   $1,025.85   $1,025.85   $1,025.80