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 $86.63   11.362%   $96.4729   $96.47   $96.45   $96.50  
  Purchase #2 $239.77   4.241%   $249.9386   $249.94   $249.95   $249.90  
  Purchase #3 $218.50   5.768%   $231.1031   $231.10   $231.10   $231.10  
  Purchase #4 $150.83   8.169%   $163.1513   $163.15   $163.15   $163.20  
  Purchase #5 $160.83   13.188%   $182.0403   $182.04   $182.05   $182.00  
  Purchase #6 $80.62   3.469%   $83.4167   $83.42   $83.40   $83.40  
  Purchase #7 $187.33   11.192%   $208.296   $208.30   $208.30   $208.30  
  7 purchase totals = $1,124.51       $1,214.4189   $1,214.42   $1,214.40   $1,214.40