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 $190.41   3.217%   $196.5355   $196.54   $196.55   $196.50  
  Purchase #2 $241.32   5.470%   $254.5202   $254.52   $254.50   $254.50  
  Purchase #3 $55.99   9.399%   $61.2525   $61.25   $61.25   $61.30  
  Purchase #4 $231.70   11.379%   $258.0651   $258.07   $258.05   $258.10  
  Purchase #5 $95.65   10.119%   $105.3288   $105.33   $105.35   $105.30  
  Purchase #6 $163.63   8.177%   $177.01   $177.01   $177.00   $177.00  
  Purchase #7 $61.47   4.225%   $64.0671   $64.07   $64.05   $64.10  
  7 purchase totals = $1,040.17       $1,116.7792   $1,116.79   $1,116.75   $1,116.80