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 $61.32   13.569%   $69.6405   $69.64   $69.65   $69.60  
  Purchase #2 $190.89   11.426%   $212.7011   $212.70   $212.70   $212.70  
  Purchase #3 $16.85   10.423%   $18.6063   $18.61   $18.60   $18.60  
  Purchase #4 $63.37   10.136%   $69.7932   $69.79   $69.80   $69.80  
  Purchase #5 $248.58   10.640%   $275.0289   $275.03   $275.05   $275.00  
  Purchase #6 $20.89   3.706%   $21.6642   $21.66   $21.65   $21.70  
  Purchase #7 $87.25   7.824%   $94.0764   $94.08   $94.10   $94.10  
  7 purchase totals = $689.15       $761.5106   $761.51   $761.55   $761.50