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 $84.42   13.314%   $95.6597   $95.66   $95.65   $95.70  
  Purchase #2 $239.58   8.640%   $260.2797   $260.28   $260.30   $260.30  
  Purchase #3 $116.93   3.141%   $120.6028   $120.60   $120.60   $120.60  
  Purchase #4 $161.66   13.115%   $182.8617   $182.86   $182.85   $182.90  
  Purchase #5 $164.40   6.507%   $175.0975   $175.10   $175.10   $175.10  
  Purchase #6 $93.37   8.616%   $101.4148   $101.41   $101.40   $101.40  
  Purchase #7 $113.71   8.175%   $123.0058   $123.01   $123.00   $123.00  
  7 purchase totals = $974.07       $1,058.9220   $1,058.92   $1,058.90   $1,059.00