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 $23.83   9.560%   $26.1081   $26.11   $26.10   $26.10  
  Purchase #2 $148.39   9.347%   $162.26   $162.26   $162.25   $162.30  
  Purchase #3 $114.95   9.613%   $126.0001   $126.00   $126.00   $126.00  
  Purchase #4 $224.37   4.484%   $234.4308   $234.43   $234.45   $234.40  
  Purchase #5 $48.92   8.582%   $53.1183   $53.12   $53.10   $53.10  
  Purchase #6 $240.84   7.828%   $259.693   $259.69   $259.70   $259.70  
  Purchase #7 $89.57   13.726%   $101.8644   $101.86   $101.85   $101.90  
  7 purchase totals = $890.87       $963.4747   $963.47   $963.45   $963.50