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 $92.61   3.300%   $95.6661   $95.67   $95.65   $95.70  
  Purchase #2 $23.69   10.144%   $26.0931   $26.09   $26.10   $26.10  
  Purchase #3 $60.26   7.366%   $64.6988   $64.70   $64.70   $64.70  
  Purchase #4 $56.87   13.601%   $64.6049   $64.60   $64.60   $64.60  
  Purchase #5 $80.43   4.471%   $84.026   $84.03   $84.05   $84.00  
  Purchase #6 $50.63   11.768%   $56.5881   $56.59   $56.60   $56.60  
  Purchase #7 $190.92   7.623%   $205.4738   $205.47   $205.45   $205.50  
  7 purchase totals = $555.41       $597.1508   $597.15   $597.15   $597.20