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 $126.92   11.592%   $141.6326   $141.63   $141.65   $141.60  
  Purchase #2 $23.55   10.599%   $26.0461   $26.05   $26.05   $26.00  
  Purchase #3 $119.42   6.874%   $127.6289   $127.63   $127.65   $127.60  
  Purchase #4 $174.69   13.219%   $197.7823   $197.78   $197.80   $197.80  
  Purchase #5 $209.48   6.873%   $223.8776   $223.88   $223.90   $223.90  
  Purchase #6 $179.78   12.291%   $201.8768   $201.88   $201.90   $201.90  
  Purchase #7 $191.83   7.287%   $205.8087   $205.81   $205.80   $205.80  
  7 purchase totals = $1,025.67       $1,124.6530   $1,124.66   $1,124.75   $1,124.60