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 $196.88   9.730%   $216.0364   $216.04   $216.05   $216.00  
  Purchase #2 $172.27   7.619%   $185.3953   $185.40   $185.40   $185.40  
  Purchase #3 $185.59   8.322%   $201.0348   $201.03   $201.05   $201.00  
  Purchase #4 $223.83   5.631%   $236.4339   $236.43   $236.45   $236.40  
  Purchase #5 $191.63   8.600%   $208.1102   $208.11   $208.10   $208.10  
  Purchase #6 $82.31   11.817%   $92.0366   $92.04   $92.05   $92.00  
  Purchase #7 $66.78   3.627%   $69.2021   $69.20   $69.20   $69.20  
  7 purchase totals = $1,119.29       $1,208.2493   $1,208.25   $1,208.30   $1,208.10