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 $69.50   7.161%   $74.4769   $74.48   $74.50   $74.50  
  Purchase #2 $153.44   6.554%   $163.4965   $163.50   $163.50   $163.50  
  Purchase #3 $205.66   3.465%   $212.7861   $212.79   $212.80   $212.80  
  Purchase #4 $180.62   9.809%   $198.337   $198.34   $198.35   $198.30  
  Purchase #5 $76.86   12.712%   $86.6304   $86.63   $86.65   $86.60  
  Purchase #6 $155.45   12.429%   $174.7709   $174.77   $174.75   $174.80  
  Purchase #7 $225.94   10.514%   $249.6953   $249.70   $249.70   $249.70  
  7 purchase totals = $1,067.47       $1,160.1931   $1,160.21   $1,160.25   $1,160.20