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 $41.27   7.167%   $44.2278   $44.23   $44.25   $44.20  
  Purchase #2 $239.35   4.175%   $249.3429   $249.34   $249.35   $249.30  
  Purchase #3 $192.25   5.844%   $203.4851   $203.49   $203.50   $203.50  
  Purchase #4 $59.59   9.199%   $65.0717   $65.07   $65.05   $65.10  
  Purchase #5 $224.31   4.615%   $234.6619   $234.66   $234.65   $234.70  
  Purchase #6 $6.72   13.429%   $7.6224   $7.62   $7.60   $7.60  
  Purchase #7 $248.56   6.617%   $265.0072   $265.01   $265.00   $265.00  
  7 purchase totals = $1,012.05       $1,069.4190   $1,069.42   $1,069.40   $1,069.40