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 $208.98   12.789%   $235.7065   $235.71   $235.70   $235.70  
  Purchase #2 $164.93   10.327%   $181.9623   $181.96   $181.95   $182.00  
  Purchase #3 $177.96   3.531%   $184.2438   $184.24   $184.25   $184.20  
  Purchase #4 $116.76   6.206%   $124.0061   $124.01   $124.00   $124.00  
  Purchase #5 $19.42   13.766%   $22.0934   $22.09   $22.10   $22.10  
  Purchase #6 $93.60   13.251%   $106.0029   $106.00   $106.00   $106.00  
  Purchase #7 $30.82   9.419%   $33.7229   $33.72   $33.70   $33.70  
  7 purchase totals = $812.47       $887.7379   $887.73   $887.70   $887.70