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 $59.54   4.527%   $62.2354   $62.24   $62.25   $62.20  
  Purchase #2 $162.35   6.330%   $172.6268   $172.63   $172.65   $172.60  
  Purchase #3 $171.56   7.139%   $183.8077   $183.81   $183.80   $183.80  
  Purchase #4 $67.47   3.502%   $69.8328   $69.83   $69.85   $69.80  
  Purchase #5 $12.59   8.120%   $13.6123   $13.61   $13.60   $13.60  
  Purchase #6 $152.33   10.377%   $168.1373   $168.14   $168.15   $168.10  
  Purchase #7 $185.91   6.335%   $197.6874   $197.69   $197.70   $197.70  
  7 purchase totals = $811.75       $867.9397   $867.95   $868.00   $867.80