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 $116.28   8.424%   $126.0754   $126.08   $126.10   $126.10  
  Purchase #2 $25.31   11.397%   $28.1946   $28.19   $28.20   $28.20  
  Purchase #3 $55.29   6.866%   $59.0862   $59.09   $59.10   $59.10  
  Purchase #4 $116.69   8.137%   $126.1851   $126.19   $126.20   $126.20  
  Purchase #5 $137.28   10.284%   $151.3979   $151.40   $151.40   $151.40  
  Purchase #6 $235.61   11.370%   $262.3989   $262.40   $262.40   $262.40  
  Purchase #7 $106.81   6.857%   $114.134   $114.13   $114.15   $114.10  
  7 purchase totals = $793.27       $867.4721   $867.48   $867.55   $867.50