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 $62.94   10.243%   $69.3869   $69.39   $69.40   $69.40  
  Purchase #2 $217.63   12.856%   $245.6085   $245.61   $245.60   $245.60  
  Purchase #3 $184.29   10.504%   $203.6478   $203.65   $203.65   $203.60  
  Purchase #4 $56.88   4.125%   $59.2263   $59.23   $59.25   $59.20  
  Purchase #5 $232.62   8.458%   $252.295   $252.30   $252.30   $252.30  
  Purchase #6 $161.64   10.341%   $178.3552   $178.36   $178.35   $178.40  
  Purchase #7 $208.56   7.741%   $224.7046   $224.70   $224.70   $224.70  
  7 purchase totals = $1,124.56       $1,233.2243   $1,233.24   $1,233.25   $1,233.20