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 $56.88   9.523%   $62.2967   $62.30   $62.30   $62.30  
  Purchase #2 $224.87   7.806%   $242.4234   $242.42   $242.40   $242.40  
  Purchase #3 $46.32   8.360%   $50.1924   $50.19   $50.20   $50.20  
  Purchase #4 $146.36   3.342%   $151.2514   $151.25   $151.25   $151.30  
  Purchase #5 $218.85   7.331%   $234.8939   $234.89   $234.90   $234.90  
  Purchase #6 $224.67   6.316%   $238.8602   $238.86   $238.85   $238.90  
  Purchase #7 $34.97   8.720%   $38.0194   $38.02   $38.00   $38.00  
  7 purchase totals = $952.92       $1,017.9374   $1,017.93   $1,017.90   $1,018.00