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 $54.66   13.553%   $62.0681   $62.07   $62.05   $62.10  
  Purchase #2 $72.70   3.522%   $75.2605   $75.26   $75.25   $75.30  
  Purchase #3 $246.42   8.325%   $266.9345   $266.93   $266.95   $266.90  
  Purchase #4 $187.73   12.808%   $211.7745   $211.77   $211.75   $211.80  
  Purchase #5 $30.67   5.264%   $32.2845   $32.28   $32.30   $32.30  
  Purchase #6 $185.63   10.585%   $205.2789   $205.28   $205.30   $205.30  
  Purchase #7 $136.60   3.806%   $141.799   $141.80   $141.80   $141.80  
  7 purchase totals = $914.41       $995.4000   $995.39   $995.40   $995.50