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 $72.36   5.205%   $76.1263   $76.13   $76.15   $76.10  
  Purchase #2 $143.77   12.617%   $161.9095   $161.91   $161.90   $161.90  
  Purchase #3 $59.69   10.163%   $65.7563   $65.76   $65.75   $65.80  
  Purchase #4 $214.68   10.690%   $237.6293   $237.63   $237.65   $237.60  
  Purchase #5 $18.46   3.224%   $19.0552   $19.06   $19.05   $19.10  
  Purchase #6 $229.73   4.871%   $240.9201   $240.92   $240.90   $240.90  
  Purchase #7 $147.61   11.672%   $164.839   $164.84   $164.85   $164.80  
  7 purchase totals = $886.30       $966.2357   $966.25   $966.25   $966.20