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 $104.71   8.246%   $113.3444   $113.34   $113.35   $113.30  
  Purchase #2 $217.43   8.408%   $235.7115   $235.71   $235.70   $235.70  
  Purchase #3 $68.73   8.636%   $74.6655   $74.67   $74.65   $74.70  
  Purchase #4 $148.48   13.766%   $168.9198   $168.92   $168.90   $168.90  
  Purchase #5 $53.90   10.599%   $59.6129   $59.61   $59.60   $59.60  
  Purchase #6 $218.25   11.564%   $243.4884   $243.49   $243.50   $243.50  
  Purchase #7 $119.32   8.400%   $129.3429   $129.34   $129.35   $129.30  
  7 purchase totals = $930.82       $1,025.0854   $1,025.08   $1,025.05   $1,025.00