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 $60.36   8.114%   $65.2576   $65.26   $65.25   $65.30  
  Purchase #2 $182.26   12.476%   $204.9988   $205.00   $205.00   $205.00  
  Purchase #3 $92.71   9.319%   $101.3496   $101.35   $101.35   $101.30  
  Purchase #4 $140.89   4.630%   $147.4132   $147.41   $147.40   $147.40  
  Purchase #5 $162.36   7.861%   $175.1231   $175.12   $175.10   $175.10  
  Purchase #6 $127.73   4.547%   $133.5379   $133.54   $133.55   $133.50  
  Purchase #7 $176.88   12.157%   $198.3833   $198.38   $198.40   $198.40  
  7 purchase totals = $943.19       $1,026.0635   $1,026.06   $1,026.05   $1,026.00