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 $107.95   5.767%   $114.1755   $114.18   $114.20   $114.20  
  Purchase #2 $17.51   13.674%   $19.9043   $19.90   $19.90   $19.90  
  Purchase #3 $103.81   5.696%   $109.723   $109.72   $109.70   $109.70  
  Purchase #4 $102.70   8.438%   $111.3658   $111.37   $111.35   $111.40  
  Purchase #5 $204.63   4.780%   $214.4113   $214.41   $214.40   $214.40  
  Purchase #6 $203.76   3.206%   $210.2925   $210.29   $210.30   $210.30  
  Purchase #7 $54.31   13.735%   $61.7695   $61.77   $61.75   $61.80  
  7 purchase totals = $794.67       $841.6419   $841.64   $841.60   $841.70