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 $68.72   7.580%   $73.929   $73.93   $73.95   $73.90  
  Purchase #2 $81.60   5.538%   $86.119   $86.12   $86.10   $86.10  
  Purchase #3 $49.56   12.461%   $55.7357   $55.74   $55.75   $55.70  
  Purchase #4 $24.35   7.798%   $26.2488   $26.25   $26.25   $26.20  
  Purchase #5 $103.62   10.197%   $114.1861   $114.19   $114.20   $114.20  
  Purchase #6 $249.40   5.849%   $263.9874   $263.99   $264.00   $264.00  
  Purchase #7 $247.95   13.320%   $280.9769   $280.98   $281.00   $281.00  
  7 purchase totals = $825.20       $901.1829   $901.20   $901.25   $901.10