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 $65.35   4.782%   $68.475   $68.48   $68.50   $68.50  
  Purchase #2 $115.66   6.773%   $123.4937   $123.49   $123.50   $123.50  
  Purchase #3 $49.99   12.247%   $56.1123   $56.11   $56.10   $56.10  
  Purchase #4 $235.84   7.302%   $253.061   $253.06   $253.05   $253.10  
  Purchase #5 $236.66   11.402%   $263.644   $263.64   $263.65   $263.60  
  Purchase #6 $6.62   9.564%   $7.2531   $7.25   $7.25   $7.30  
  Purchase #7 $141.36   8.154%   $152.8865   $152.89   $152.90   $152.90  
  7 purchase totals = $851.48       $924.9256   $924.92   $924.95   $925.00