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 $212.26   11.722%   $237.1411   $237.14   $237.15   $237.10  
  Purchase #2 $227.37   10.127%   $250.3958   $250.40   $250.40   $250.40  
  Purchase #3 $83.93   13.401%   $95.1775   $95.18   $95.20   $95.20  
  Purchase #4 $42.45   3.598%   $43.9774   $43.98   $44.00   $44.00  
  Purchase #5 $207.88   10.814%   $230.3601   $230.36   $230.35   $230.40  
  Purchase #6 $71.28   10.286%   $78.6119   $78.61   $78.60   $78.60  
  Purchase #7 $164.28   4.547%   $171.7498   $171.75   $171.75   $171.70  
  7 purchase totals = $1,009.45       $1,107.4136   $1,107.42   $1,107.45   $1,107.40