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 $82.89   4.137%   $86.3192   $86.32   $86.30   $86.30  
  Purchase #2 $178.61   13.439%   $202.6134   $202.61   $202.60   $202.60  
  Purchase #3 $214.95   3.129%   $221.6758   $221.68   $221.70   $221.70  
  Purchase #4 $24.28   9.653%   $26.6237   $26.62   $26.60   $26.60  
  Purchase #5 $197.94   3.418%   $204.7056   $204.71   $204.70   $204.70  
  Purchase #6 $201.89   3.390%   $208.7341   $208.73   $208.75   $208.70  
  Purchase #7 $243.37   10.171%   $268.1232   $268.12   $268.10   $268.10  
  7 purchase totals = $1,143.93       $1,218.7950   $1,218.79   $1,218.75   $1,218.70