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 $93.67   11.703%   $104.6322   $104.63   $104.65   $104.60  
  Purchase #2 $55.34   10.235%   $61.004   $61.00   $61.00   $61.00  
  Purchase #3 $82.79   4.121%   $86.2018   $86.20   $86.20   $86.20  
  Purchase #4 $9.61   6.772%   $10.2608   $10.26   $10.25   $10.30  
  Purchase #5 $44.36   7.291%   $47.5943   $47.59   $47.60   $47.60  
  Purchase #6 $73.34   4.289%   $76.4856   $76.49   $76.50   $76.50  
  Purchase #7 $86.59   4.684%   $90.6459   $90.65   $90.65   $90.60  
  7 purchase totals = $445.70       $476.8246   $476.82   $476.85   $476.80