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 $185.83   9.628%   $203.7217   $203.72   $203.70   $203.70  
  Purchase #2 $242.32   8.264%   $262.3453   $262.35   $262.35   $262.30  
  Purchase #3 $164.73   10.329%   $181.745   $181.75   $181.75   $181.70  
  Purchase #4 $163.67   3.794%   $169.8796   $169.88   $169.90   $169.90  
  Purchase #5 $231.99   6.196%   $246.3641   $246.36   $246.35   $246.40  
  Purchase #6 $81.41   7.843%   $87.795   $87.80   $87.80   $87.80  
  Purchase #7 $95.47   12.783%   $107.6739   $107.67   $107.65   $107.70  
  7 purchase totals = $1,165.42       $1,259.5246   $1,259.53   $1,259.50   $1,259.50