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 $60.84   13.788%   $69.2286   $69.23   $69.25   $69.20  
  Purchase #2 $217.63   8.828%   $236.8424   $236.84   $236.85   $236.80  
  Purchase #3 $152.71   12.656%   $172.037   $172.04   $172.05   $172.00  
  Purchase #4 $239.33   4.423%   $249.9156   $249.92   $249.90   $249.90  
  Purchase #5 $27.76   8.602%   $30.1479   $30.15   $30.15   $30.10  
  Purchase #6 $147.40   9.213%   $160.98   $160.98   $161.00   $161.00  
  Purchase #7 $227.64   5.587%   $240.3582   $240.36   $240.35   $240.40  
  7 purchase totals = $1,073.31       $1,159.5097   $1,159.52   $1,159.55   $1,159.40