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 $70.49   7.769%   $75.9664   $75.97   $75.95   $76.00  
  Purchase #2 $65.46   12.369%   $73.5567   $73.56   $73.55   $73.60  
  Purchase #3 $174.36   7.143%   $186.8145   $186.81   $186.80   $186.80  
  Purchase #4 $148.58   6.497%   $158.2332   $158.23   $158.25   $158.20  
  Purchase #5 $70.49   10.584%   $77.9507   $77.95   $77.95   $78.00  
  Purchase #6 $168.68   3.563%   $174.6901   $174.69   $174.70   $174.70  
  Purchase #7 $36.98   10.139%   $40.7294   $40.73   $40.75   $40.70  
  7 purchase totals = $735.04       $787.9410   $787.94   $787.95   $788.00