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 $188.66   5.603%   $199.2306   $199.23   $199.25   $199.20  
  Purchase #2 $187.82   10.239%   $207.0509   $207.05   $207.05   $207.10  
  Purchase #3 $153.30   7.210%   $164.3529   $164.35   $164.35   $164.40  
  Purchase #4 $32.65   12.389%   $36.695   $36.70   $36.70   $36.70  
  Purchase #5 $210.48   5.837%   $222.7657   $222.77   $222.75   $222.80  
  Purchase #6 $201.63   8.680%   $219.1315   $219.13   $219.15   $219.10  
  Purchase #7 $143.73   6.124%   $152.532   $152.53   $152.55   $152.50  
  7 purchase totals = $1,118.27       $1,201.7586   $1,201.76   $1,201.80   $1,201.80