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 $61.69   11.799%   $68.9688   $68.97   $68.95   $69.00  
  Purchase #2 $83.65   4.496%   $87.4109   $87.41   $87.40   $87.40  
  Purchase #3 $181.71   13.720%   $206.6406   $206.64   $206.65   $206.60  
  Purchase #4 $211.81   4.102%   $220.4984   $220.50   $220.50   $220.50  
  Purchase #5 $242.36   12.467%   $272.575   $272.58   $272.60   $272.60  
  Purchase #6 $117.44   11.493%   $130.9374   $130.94   $130.95   $130.90  
  Purchase #7 $181.86   3.373%   $187.9941   $187.99   $188.00   $188.00  
  7 purchase totals = $1,080.52       $1,175.0252   $1,175.03   $1,175.05   $1,175.00