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 $41.95   5.856%   $44.4066   $44.41   $44.40   $44.40  
  Purchase #2 $174.67   7.486%   $187.7458   $187.75   $187.75   $187.70  
  Purchase #3 $224.70   13.183%   $254.3222   $254.32   $254.30   $254.30  
  Purchase #4 $50.98   9.569%   $55.8583   $55.86   $55.85   $55.90  
  Purchase #5 $158.77   3.333%   $164.0618   $164.06   $164.05   $164.10  
  Purchase #6 $214.76   8.762%   $233.5773   $233.58   $233.60   $233.60  
  Purchase #7 $7.48   12.104%   $8.3854   $8.39   $8.40   $8.40  
  7 purchase totals = $873.31       $948.3574   $948.37   $948.35   $948.40