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 $62.94   3.669%   $65.2493   $65.25   $65.25   $65.20  
  Purchase #2 $220.82   12.794%   $249.0717   $249.07   $249.05   $249.10  
  Purchase #3 $242.97   10.252%   $267.8793   $267.88   $267.90   $267.90  
  Purchase #4 $221.43   13.146%   $250.5392   $250.54   $250.55   $250.50  
  Purchase #5 $168.91   6.479%   $179.8537   $179.85   $179.85   $179.90  
  Purchase #6 $242.69   8.470%   $263.2458   $263.25   $263.25   $263.20  
  Purchase #7 $109.50   8.110%   $118.3805   $118.38   $118.40   $118.40  
  7 purchase totals = $1,269.26       $1,394.2195   $1,394.22   $1,394.25   $1,394.20