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 $191.53   13.658%   $217.6892   $217.69   $217.70   $217.70  
  Purchase #2 $30.93   9.315%   $33.8111   $33.81   $33.80   $33.80  
  Purchase #3 $72.97   5.571%   $77.0352   $77.04   $77.05   $77.00  
  Purchase #4 $88.83   5.779%   $93.9635   $93.96   $93.95   $94.00  
  Purchase #5 $136.77   13.859%   $155.725   $155.73   $155.75   $155.70  
  Purchase #6 $14.55   7.759%   $15.6789   $15.68   $15.70   $15.70  
  Purchase #7 $160.45   11.586%   $179.0397   $179.04   $179.05   $179.00  
  7 purchase totals = $696.03       $772.9426   $772.95   $773.00   $772.90