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 $194.54   5.660%   $205.551   $205.55   $205.55   $205.60  
  Purchase #2 $126.68   6.414%   $134.8053   $134.81   $134.80   $134.80  
  Purchase #3 $167.58   3.560%   $173.5458   $173.55   $173.55   $173.50  
  Purchase #4 $124.50   12.121%   $139.5906   $139.59   $139.60   $139.60  
  Purchase #5 $164.83   6.663%   $175.8126   $175.81   $175.80   $175.80  
  Purchase #6 $9.90   10.664%   $10.9557   $10.96   $10.95   $11.00  
  Purchase #7 $167.55   6.571%   $178.5597   $178.56   $178.55   $178.60  
  7 purchase totals = $955.58       $1,018.8207   $1,018.83   $1,018.80   $1,018.90