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 $218.53   7.604%   $235.147   $235.15   $235.15   $235.10  
  Purchase #2 $30.45   9.859%   $33.4521   $33.45   $33.45   $33.50  
  Purchase #3 $24.47   6.584%   $26.0811   $26.08   $26.10   $26.10  
  Purchase #4 $167.91   7.459%   $180.4344   $180.43   $180.45   $180.40  
  Purchase #5 $32.68   9.496%   $35.7833   $35.78   $35.80   $35.80  
  Purchase #6 $41.64   3.396%   $43.0541   $43.05   $43.05   $43.10  
  Purchase #7 $198.81   4.696%   $208.1461   $208.15   $208.15   $208.10  
  7 purchase totals = $714.49       $762.0981   $762.09   $762.15   $762.10