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 $84.30   12.749%   $95.0474   $95.05   $95.05   $95.00  
  Purchase #2 $70.59   11.673%   $78.83   $78.83   $78.85   $78.80  
  Purchase #3 $249.27   3.291%   $257.4735   $257.47   $257.45   $257.50  
  Purchase #4 $57.50   4.338%   $59.9944   $59.99   $60.00   $60.00  
  Purchase #5 $53.57   10.734%   $59.3202   $59.32   $59.30   $59.30  
  Purchase #6 $217.77   4.143%   $226.7922   $226.79   $226.80   $226.80  
  Purchase #7 $185.91   10.372%   $205.1926   $205.19   $205.20   $205.20  
  7 purchase totals = $918.91       $982.6503   $982.64   $982.65   $982.60