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 $206.53   3.594%   $213.9527   $213.95   $213.95   $214.00  
  Purchase #2 $60.87   9.201%   $66.4706   $66.47   $66.45   $66.50  
  Purchase #3 $100.45   7.121%   $107.603   $107.60   $107.60   $107.60  
  Purchase #4 $114.88   6.412%   $122.2461   $122.25   $122.25   $122.20  
  Purchase #5 $126.50   8.316%   $137.0197   $137.02   $137.00   $137.00  
  Purchase #6 $39.81   11.263%   $44.2938   $44.29   $44.30   $44.30  
  Purchase #7 $215.81   11.455%   $240.531   $240.53   $240.55   $240.50  
  7 purchase totals = $864.85       $932.1169   $932.11   $932.10   $932.10