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 $54.46   13.815%   $61.9836   $61.98   $62.00   $62.00  
  Purchase #2 $164.42   8.641%   $178.6275   $178.63   $178.65   $178.60  
  Purchase #3 $5.97   4.461%   $6.2363   $6.24   $6.25   $6.20  
  Purchase #4 $208.76   6.165%   $221.6301   $221.63   $221.65   $221.60  
  Purchase #5 $126.51   4.694%   $132.4484   $132.45   $132.45   $132.40  
  Purchase #6 $56.66   10.348%   $62.5232   $62.52   $62.50   $62.50  
  Purchase #7 $36.85   11.654%   $41.1445   $41.14   $41.15   $41.10  
  7 purchase totals = $653.63       $704.5936   $704.59   $704.65   $704.40