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 $68.28   11.368%   $76.0421   $76.04   $76.05   $76.00  
  Purchase #2 $176.72   4.338%   $184.3861   $184.39   $184.40   $184.40  
  Purchase #3 $16.36   4.651%   $17.1209   $17.12   $17.10   $17.10  
  Purchase #4 $197.89   12.484%   $222.5946   $222.59   $222.60   $222.60  
  Purchase #5 $116.35   10.808%   $128.9251   $128.93   $128.95   $128.90  
  Purchase #6 $221.85   5.641%   $234.3646   $234.36   $234.35   $234.40  
  Purchase #7 $5.75   5.550%   $6.0691   $6.07   $6.05   $6.10  
  7 purchase totals = $803.20       $869.5025   $869.50   $869.50   $869.50