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 $243.53   7.574%   $261.975   $261.98   $262.00   $262.00  
  Purchase #2 $119.54   10.687%   $132.3152   $132.32   $132.30   $132.30  
  Purchase #3 $233.82   4.591%   $244.5547   $244.55   $244.55   $244.60  
  Purchase #4 $112.32   6.659%   $119.7994   $119.80   $119.80   $119.80  
  Purchase #5 $146.83   11.467%   $163.667   $163.67   $163.65   $163.70  
  Purchase #6 $173.33   10.202%   $191.0131   $191.01   $191.00   $191.00  
  Purchase #7 $231.46   10.705%   $256.2378   $256.24   $256.25   $256.20  
  7 purchase totals = $1,260.83       $1,369.5622   $1,369.57   $1,369.55   $1,369.60