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 $146.83   12.225%   $164.78   $164.78   $164.80   $164.80  
  Purchase #2 $105.95   5.244%   $111.506   $111.51   $111.50   $111.50  
  Purchase #3 $117.90   6.847%   $125.9726   $125.97   $125.95   $126.00  
  Purchase #4 $219.32   13.354%   $248.608   $248.61   $248.60   $248.60  
  Purchase #5 $214.77   4.298%   $224.0008   $224.00   $224.00   $224.00  
  Purchase #6 $65.64   7.849%   $70.7921   $70.79   $70.80   $70.80  
  Purchase #7 $82.56   4.832%   $86.5493   $86.55   $86.55   $86.50  
  7 purchase totals = $952.97       $1,032.2088   $1,032.21   $1,032.20   $1,032.20