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 $201.86   3.170%   $208.259   $208.26   $208.25   $208.30  
  Purchase #2 $164.40   9.418%   $179.8832   $179.88   $179.90   $179.90  
  Purchase #3 $52.26   13.640%   $59.3883   $59.39   $59.40   $59.40  
  Purchase #4 $215.75   6.722%   $230.2527   $230.25   $230.25   $230.30  
  Purchase #5 $48.25   5.855%   $51.075   $51.08   $51.10   $51.10  
  Purchase #6 $201.43   6.565%   $214.6539   $214.65   $214.65   $214.70  
  Purchase #7 $147.77   10.797%   $163.7247   $163.72   $163.70   $163.70  
  7 purchase totals = $1,031.72       $1,107.2368   $1,107.23   $1,107.25   $1,107.40