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 $162.91   8.582%   $176.8909   $176.89   $176.90   $176.90  
  Purchase #2 $54.48   13.249%   $61.6981   $61.70   $61.70   $61.70  
  Purchase #3 $247.33   6.211%   $262.6917   $262.69   $262.70   $262.70  
  Purchase #4 $118.50   5.682%   $125.2332   $125.23   $125.25   $125.20  
  Purchase #5 $164.43   3.742%   $170.583   $170.58   $170.60   $170.60  
  Purchase #6 $112.29   9.528%   $122.989   $122.99   $123.00   $123.00  
  Purchase #7 $127.93   5.494%   $134.9585   $134.96   $134.95   $135.00  
  7 purchase totals = $987.87       $1,055.0444   $1,055.04   $1,055.10   $1,055.10