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 $193.92   3.794%   $201.2773   $201.28   $201.30   $201.30  
  Purchase #2 $37.32   6.704%   $39.8219   $39.82   $39.80   $39.80  
  Purchase #3 $185.62   5.611%   $196.0351   $196.04   $196.05   $196.00  
  Purchase #4 $24.73   6.801%   $26.4119   $26.41   $26.40   $26.40  
  Purchase #5 $159.78   3.217%   $164.9201   $164.92   $164.90   $164.90  
  Purchase #6 $81.35   3.853%   $84.4844   $84.48   $84.50   $84.50  
  Purchase #7 $159.60   7.807%   $172.06   $172.06   $172.05   $172.10  
  7 purchase totals = $842.32       $885.0107   $885.01   $885.00   $885.00