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 $62.99   4.284%   $65.6885   $65.69   $65.70   $65.70  
  Purchase #2 $101.73   6.589%   $108.433   $108.43   $108.45   $108.40  
  Purchase #3 $60.57   4.640%   $63.3804   $63.38   $63.40   $63.40  
  Purchase #4 $178.26   11.114%   $198.0718   $198.07   $198.05   $198.10  
  Purchase #5 $126.37   6.228%   $134.2403   $134.24   $134.25   $134.20  
  Purchase #6 $175.56   9.778%   $192.7263   $192.73   $192.75   $192.70  
  Purchase #7 $22.41   9.177%   $24.4666   $24.47   $24.45   $24.50  
  7 purchase totals = $727.89       $787.0069   $787.01   $787.05   $787.00