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 $180.81   13.721%   $205.6189   $205.62   $205.60   $205.60  
  Purchase #2 $211.97   11.756%   $236.8892   $236.89   $236.90   $236.90  
  Purchase #3 $143.43   12.601%   $161.5036   $161.50   $161.50   $161.50  
  Purchase #4 $249.96   5.308%   $263.2279   $263.23   $263.25   $263.20  
  Purchase #5 $106.95   5.264%   $112.5798   $112.58   $112.60   $112.60  
  Purchase #6 $124.63   3.691%   $129.2301   $129.23   $129.25   $129.20  
  Purchase #7 $249.51   11.259%   $277.6023   $277.60   $277.60   $277.60  
  7 purchase totals = $1,267.26       $1,386.6518   $1,386.65   $1,386.70   $1,386.60