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 $59.42   12.789%   $67.0192   $67.02   $67.00   $67.00  
  Purchase #2 $192.40   11.284%   $214.1104   $214.11   $214.10   $214.10  
  Purchase #3 $218.88   11.198%   $243.3902   $243.39   $243.40   $243.40  
  Purchase #4 $11.84   3.543%   $12.2595   $12.26   $12.25   $12.30  
  Purchase #5 $207.27   10.661%   $229.3671   $229.37   $229.35   $229.40  
  Purchase #6 $196.80   7.792%   $212.1347   $212.13   $212.15   $212.10  
  Purchase #7 $234.73   11.602%   $261.9634   $261.96   $261.95   $262.00  
  7 purchase totals = $1,121.34       $1,240.2445   $1,240.24   $1,240.20   $1,240.30