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 $70.81   6.843%   $75.6555   $75.66   $75.65   $75.70  
  Purchase #2 $142.25   8.686%   $154.6058   $154.61   $154.60   $154.60  
  Purchase #3 $162.35   10.353%   $179.1581   $179.16   $179.15   $179.20  
  Purchase #4 $244.29   6.766%   $260.8187   $260.82   $260.80   $260.80  
  Purchase #5 $206.88   3.455%   $214.0277   $214.03   $214.05   $214.00  
  Purchase #6 $72.76   4.184%   $75.8043   $75.80   $75.80   $75.80  
  Purchase #7 $196.34   6.235%   $208.5818   $208.58   $208.60   $208.60  
  7 purchase totals = $1,095.68       $1,168.6519   $1,168.66   $1,168.65   $1,168.70