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 $164.82   13.225%   $186.6174   $186.62   $186.60   $186.60  
  Purchase #2 $23.87   8.419%   $25.8796   $25.88   $25.90   $25.90  
  Purchase #3 $35.72   5.326%   $37.6224   $37.62   $37.60   $37.60  
  Purchase #4 $21.91   9.237%   $23.9338   $23.93   $23.95   $23.90  
  Purchase #5 $175.93   9.600%   $192.8193   $192.82   $192.80   $192.80  
  Purchase #6 $237.26   10.594%   $262.3953   $262.40   $262.40   $262.40  
  Purchase #7 $218.67   3.543%   $226.4175   $226.42   $226.40   $226.40  
  7 purchase totals = $878.18       $955.6853   $955.69   $955.65   $955.60