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 $68.32   11.633%   $76.2677   $76.27   $76.25   $76.30  
  Purchase #2 $166.94   7.320%   $179.16   $179.16   $179.15   $179.20  
  Purchase #3 $177.44   12.737%   $200.0405   $200.04   $200.05   $200.00  
  Purchase #4 $93.69   7.231%   $100.4647   $100.46   $100.45   $100.50  
  Purchase #5 $224.25   10.206%   $247.137   $247.14   $247.15   $247.10  
  Purchase #6 $83.91   3.204%   $86.5985   $86.60   $86.60   $86.60  
  Purchase #7 $135.57   7.354%   $145.5398   $145.54   $145.55   $145.50  
  7 purchase totals = $950.12       $1,035.2082   $1,035.21   $1,035.20   $1,035.20