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 $62.40   4.544%   $65.2355   $65.24   $65.25   $65.20  
  Purchase #2 $195.55   10.358%   $215.8051   $215.81   $215.80   $215.80  
  Purchase #3 $235.97   3.867%   $245.095   $245.10   $245.10   $245.10  
  Purchase #4 $207.84   4.672%   $217.5503   $217.55   $217.55   $217.60  
  Purchase #5 $221.53   6.149%   $235.1519   $235.15   $235.15   $235.20  
  Purchase #6 $234.52   11.386%   $261.2224   $261.22   $261.20   $261.20  
  Purchase #7 $236.43   7.395%   $253.914   $253.91   $253.90   $253.90  
  7 purchase totals = $1,394.24       $1,493.9742   $1,493.98   $1,493.95   $1,494.00