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 $187.52   11.370%   $208.841   $208.84   $208.85   $208.80  
  Purchase #2 $110.56   7.691%   $119.0632   $119.06   $119.05   $119.10  
  Purchase #3 $83.30   3.728%   $86.4054   $86.41   $86.40   $86.40  
  Purchase #4 $226.32   6.321%   $240.6257   $240.63   $240.65   $240.60  
  Purchase #5 $238.46   6.321%   $253.5331   $253.53   $253.55   $253.50  
  Purchase #6 $114.90   9.583%   $125.9109   $125.91   $125.90   $125.90  
  Purchase #7 $78.52   5.396%   $82.7569   $82.76   $82.75   $82.80  
  7 purchase totals = $1,039.58       $1,117.1362   $1,117.14   $1,117.15   $1,117.10