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 $82.96   11.690%   $92.658   $92.66   $92.65   $92.70  
  Purchase #2 $207.90   12.139%   $233.137   $233.14   $233.15   $233.10  
  Purchase #3 $49.99   13.194%   $56.5857   $56.59   $56.60   $56.60  
  Purchase #4 $221.38   11.167%   $246.1015   $246.10   $246.10   $246.10  
  Purchase #5 $95.25   4.666%   $99.6944   $99.69   $99.70   $99.70  
  Purchase #6 $74.36   4.280%   $77.5426   $77.54   $77.55   $77.50  
  Purchase #7 $168.79   7.277%   $181.0728   $181.07   $181.05   $181.10  
  7 purchase totals = $900.63       $986.7920   $986.79   $986.80   $986.80