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 $216.57   8.506%   $234.9914   $234.99   $235.00   $235.00  
  Purchase #2 $237.46   13.478%   $269.4649   $269.46   $269.45   $269.50  
  Purchase #3 $184.42   12.388%   $207.2659   $207.27   $207.25   $207.30  
  Purchase #4 $61.35   12.387%   $68.9494   $68.95   $68.95   $68.90  
  Purchase #5 $228.93   9.358%   $250.3533   $250.35   $250.35   $250.40  
  Purchase #6 $216.49   9.193%   $236.3919   $236.39   $236.40   $236.40  
  Purchase #7 $165.78   12.250%   $186.0881   $186.09   $186.10   $186.10  
  7 purchase totals = $1,311.00       $1,453.5049   $1,453.50   $1,453.50   $1,453.60