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 $207.97   3.228%   $214.6833   $214.68   $214.70   $214.70  
  Purchase #2 $90.27   4.557%   $94.3836   $94.38   $94.40   $94.40  
  Purchase #3 $179.45   13.396%   $203.4891   $203.49   $203.50   $203.50  
  Purchase #4 $154.63   13.579%   $175.6272   $175.63   $175.65   $175.60  
  Purchase #5 $229.32   12.144%   $257.1686   $257.17   $257.15   $257.20  
  Purchase #6 $226.76   12.745%   $255.6606   $255.66   $255.65   $255.70  
  Purchase #7 $234.93   3.652%   $243.5096   $243.51   $243.50   $243.50  
  7 purchase totals = $1,323.33       $1,444.5220   $1,444.52   $1,444.55   $1,444.60