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 $61.94   9.821%   $68.0231   $68.02   $68.00   $68.00  
  Purchase #2 $148.99   3.167%   $153.7085   $153.71   $153.70   $153.70  
  Purchase #3 $59.32   12.230%   $66.5748   $66.57   $66.55   $66.60  
  Purchase #4 $48.82   8.705%   $53.0698   $53.07   $53.05   $53.10  
  Purchase #5 $97.59   13.642%   $110.9032   $110.90   $110.90   $110.90  
  Purchase #6 $70.78   8.675%   $76.9202   $76.92   $76.90   $76.90  
  Purchase #7 $190.85   8.502%   $207.0761   $207.08   $207.10   $207.10  
  7 purchase totals = $678.29       $736.2757   $736.27   $736.20   $736.30