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 $247.55   5.869%   $262.0787   $262.08   $262.10   $262.10  
  Purchase #2 $140.62   3.755%   $145.9003   $145.90   $145.90   $145.90  
  Purchase #3 $248.32   4.683%   $259.9488   $259.95   $259.95   $259.90  
  Purchase #4 $76.96   7.793%   $82.9575   $82.96   $82.95   $83.00  
  Purchase #5 $8.85   13.468%   $10.0419   $10.04   $10.05   $10.00  
  Purchase #6 $45.89   6.691%   $48.9605   $48.96   $48.95   $49.00  
  Purchase #7 $219.69   6.729%   $234.4729   $234.47   $234.45   $234.50  
  7 purchase totals = $987.88       $1,044.3606   $1,044.36   $1,044.35   $1,044.40