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 $65.45   8.605%   $71.082   $71.08   $71.10   $71.10  
  Purchase #2 $161.83   3.631%   $167.706   $167.71   $167.70   $167.70  
  Purchase #3 $81.93   13.804%   $93.2396   $93.24   $93.25   $93.20  
  Purchase #4 $50.81   12.207%   $57.0124   $57.01   $57.00   $57.00  
  Purchase #5 $212.85   11.646%   $237.6385   $237.64   $237.65   $237.60  
  Purchase #6 $129.65   8.457%   $140.6145   $140.61   $140.60   $140.60  
  Purchase #7 $233.77   7.868%   $252.163   $252.16   $252.15   $252.20  
  7 purchase totals = $936.29       $1,019.4560   $1,019.45   $1,019.45   $1,019.40