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 $152.94   3.433%   $158.1904   $158.19   $158.20   $158.20  
  Purchase #2 $176.62   10.220%   $194.6706   $194.67   $194.65   $194.70  
  Purchase #3 $231.67   8.818%   $252.0987   $252.10   $252.10   $252.10  
  Purchase #4 $176.54   3.336%   $182.4294   $182.43   $182.45   $182.40  
  Purchase #5 $43.95   11.256%   $48.897   $48.90   $48.90   $48.90  
  Purchase #6 $57.40   5.532%   $60.5754   $60.58   $60.60   $60.60  
  Purchase #7 $180.61   11.426%   $201.2465   $201.25   $201.25   $201.20  
  7 purchase totals = $1,019.73       $1,098.1080   $1,098.12   $1,098.15   $1,098.10