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 $76.59   11.297%   $85.2424   $85.24   $85.25   $85.20  
  Purchase #2 $165.89   12.533%   $186.681   $186.68   $186.70   $186.70  
  Purchase #3 $43.28   5.167%   $45.5163   $45.52   $45.50   $45.50  
  Purchase #4 $145.39   6.846%   $155.3434   $155.34   $155.35   $155.30  
  Purchase #5 $208.26   3.198%   $214.9202   $214.92   $214.90   $214.90  
  Purchase #6 $173.81   11.403%   $193.6296   $193.63   $193.65   $193.60  
  Purchase #7 $107.43   6.658%   $114.5827   $114.58   $114.60   $114.60  
  7 purchase totals = $920.65       $995.9156   $995.91   $995.95   $995.80