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 $119.34   6.377%   $126.9503   $126.95   $126.95   $127.00  
  Purchase #2 $5.78   7.832%   $6.2327   $6.23   $6.25   $6.20  
  Purchase #3 $213.52   6.844%   $228.1333   $228.13   $228.15   $228.10  
  Purchase #4 $189.69   10.495%   $209.598   $209.60   $209.60   $209.60  
  Purchase #5 $161.41   5.639%   $170.5119   $170.51   $170.50   $170.50  
  Purchase #6 $13.53   5.639%   $14.293   $14.29   $14.30   $14.30  
  Purchase #7 $234.36   6.358%   $249.2606   $249.26   $249.25   $249.30  
  7 purchase totals = $937.63       $1,004.9798   $1,004.97   $1,005.00   $1,005.00