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 $208.71   3.656%   $216.3404   $216.34   $216.35   $216.30  
  Purchase #2 $191.93   11.794%   $214.5662   $214.57   $214.55   $214.60  
  Purchase #3 $182.39   4.679%   $190.924   $190.92   $190.90   $190.90  
  Purchase #4 $61.35   5.505%   $64.7273   $64.73   $64.75   $64.70  
  Purchase #5 $180.98   11.142%   $201.1448   $201.14   $201.15   $201.10  
  Purchase #6 $86.79   8.244%   $93.945   $93.95   $93.95   $93.90  
  Purchase #7 $236.56   6.571%   $252.1044   $252.10   $252.10   $252.10  
  7 purchase totals = $1,148.71       $1,233.7521   $1,233.75   $1,233.75   $1,233.60