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 $208.27   3.213%   $214.9617   $214.96   $214.95   $215.00  
  Purchase #2 $233.81   9.437%   $255.8746   $255.87   $255.85   $255.90  
  Purchase #3 $17.28   5.515%   $18.233   $18.23   $18.25   $18.20  
  Purchase #4 $238.79   5.624%   $252.2195   $252.22   $252.20   $252.20  
  Purchase #5 $133.78   6.506%   $142.4837   $142.48   $142.50   $142.50  
  Purchase #6 $141.84   3.574%   $146.9094   $146.91   $146.90   $146.90  
  Purchase #7 $167.81   4.869%   $175.9807   $175.98   $176.00   $176.00  
  7 purchase totals = $1,141.58       $1,206.6626   $1,206.65   $1,206.65   $1,206.70