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 $175.48   11.475%   $195.6163   $195.62   $195.60   $195.60  
  Purchase #2 $154.28   13.381%   $174.9242   $174.92   $174.90   $174.90  
  Purchase #3 $154.63   6.468%   $164.6315   $164.63   $164.65   $164.60  
  Purchase #4 $66.49   10.670%   $73.5845   $73.58   $73.60   $73.60  
  Purchase #5 $54.46   9.774%   $59.7829   $59.78   $59.80   $59.80  
  Purchase #6 $114.29   4.409%   $119.329   $119.33   $119.35   $119.30  
  Purchase #7 $211.33   13.122%   $239.0607   $239.06   $239.05   $239.10  
  7 purchase totals = $930.96       $1,026.9291   $1,026.92   $1,026.95   $1,026.90