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 $88.64   7.702%   $95.4671   $95.47   $95.45   $95.50  
  Purchase #2 $120.33   11.284%   $133.908   $133.91   $133.90   $133.90  
  Purchase #3 $32.43   9.218%   $35.4194   $35.42   $35.40   $35.40  
  Purchase #4 $187.78   4.733%   $196.6676   $196.67   $196.65   $196.70  
  Purchase #5 $103.68   6.260%   $110.1704   $110.17   $110.15   $110.20  
  Purchase #6 $242.96   10.761%   $269.1049   $269.10   $269.10   $269.10  
  Purchase #7 $235.45   9.325%   $257.4057   $257.41   $257.40   $257.40  
  7 purchase totals = $1,011.27       $1,098.1431   $1,098.15   $1,098.05   $1,098.20