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 $208.72   7.590%   $224.5618   $224.56   $224.55   $224.60  
  Purchase #2 $51.73   8.534%   $56.1446   $56.14   $56.15   $56.10  
  Purchase #3 $113.63   3.513%   $117.6218   $117.62   $117.60   $117.60  
  Purchase #4 $118.69   10.435%   $131.0753   $131.08   $131.10   $131.10  
  Purchase #5 $197.46   4.505%   $206.3556   $206.36   $206.35   $206.40  
  Purchase #6 $119.77   12.213%   $134.3975   $134.40   $134.40   $134.40  
  Purchase #7 $196.81   5.611%   $207.853   $207.85   $207.85   $207.90  
  7 purchase totals = $1,006.81       $1,078.0096   $1,078.01   $1,078.00   $1,078.10