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 $87.41   5.193%   $91.9492   $91.95   $91.95   $91.90  
  Purchase #2 $130.58   4.514%   $136.4744   $136.47   $136.45   $136.50  
  Purchase #3 $204.38   5.331%   $215.2755   $215.28   $215.30   $215.30  
  Purchase #4 $46.62   10.252%   $51.3995   $51.40   $51.40   $51.40  
  Purchase #5 $200.45   13.618%   $227.7473   $227.75   $227.75   $227.70  
  Purchase #6 $74.90   3.237%   $77.3245   $77.32   $77.30   $77.30  
  Purchase #7 $13.68   3.157%   $14.1119   $14.11   $14.10   $14.10  
  7 purchase totals = $758.02       $814.2823   $814.28   $814.25   $814.20