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 $113.41   11.265%   $126.1856   $126.19   $126.20   $126.20  
  Purchase #2 $74.63   4.574%   $78.0436   $78.04   $78.05   $78.00  
  Purchase #3 $43.47   10.599%   $48.0774   $48.08   $48.10   $48.10  
  Purchase #4 $177.92   11.668%   $198.6797   $198.68   $198.70   $198.70  
  Purchase #5 $86.89   10.766%   $96.2446   $96.24   $96.25   $96.20  
  Purchase #6 $168.64   6.276%   $179.2238   $179.22   $179.20   $179.20  
  Purchase #7 $201.56   3.323%   $208.2578   $208.26   $208.25   $208.30  
  7 purchase totals = $866.52       $934.7125   $934.71   $934.75   $934.70